Method for forming nickel silicide film, method for manufacturing semiconductor device, and method for etching nickel silicide

ABSTRACT

A method for manufacturing a semiconductor device, which comprises a laminate film forming step of laminating one or more nickel layers and one or more silicon layers alternately on a substrate having, on its surface, a semiconductor region and an insulating film region at a first substrate temperature not causing a silicide forming reaction, a silicide reaction step of subjecting the laminate film to a heat treatment at a second substrate temperature suitable for forming nickel monosilicide, and a step of removing a film having been formed on the insulating film region by wet etching, wherein in the laminate film forming step, the ratio of the number of nickel atoms to that of silicon atoms in the whole laminate film is set to be 1 or more; a method for forming a nickel silicide film which is included in the above method for manufacturing a semiconductor device: and a method for etching a nickel silicide film. The above method allows the formation of a nickel silicide film of a low resistance having a satisfactory thickness with the minimum consumption of silicon atoms in a silicon substrate.

FIELD OF THE INVENTION

The present invention relates to a nickel silicide formation method, asemiconductor device fabrication method, and a nickel silicide etchingmethod, and, more particularly to a nickel silicide formation method inwhich the nickel silicide has a sufficient thickness and a lowresistivity, a semiconductor device fabrication method using the nickelsilicide formation method, and a selective etching method of a nickelsilicide film having a nickel-rich composition.

BACKGROUND OF THE INVENTION

All of patents, patent applications, patent publications, scientificarticles and the like, which will hereinafter be cited or identified inthe present application, will hereby be incorporated by references intheir entirety in order to describe more fully the state of the art, towhich the present invention pertains.

Conventionally, a metal silicide which is a chemical compound of metaland silicon has been used as a contact material to a source/drain regionand a gate electrode of a silicon MOS transistor. In metal silicides,especially, titanium silicide (TiSi₂) and cobalt silicide (CoSi₂) hasbeen known to have a low resistivity and a low shottky barrier againstsilicon, thereby currently widely being used for various types of LSI.

In addition, recently, with a progress of miniaturization of a MOStransistor, thereby a progress of thinning of the source/drain region,there has been a movement to use nickel monosilicide (NiSi) for thecontact material. This is because of the following reasons. NiSi has acapability of forming a metal silicide film with less silicon atoms thanTiSi₂ and CoSi₂ for forming the same thickness film when it is formed bythe reaction of silicon atoms of the substrate with the metal atomsdeposited on the substrate. Therefore, it becomes possible to decrease aresistance of the silicide film without degrading a junction leakcharacteristic. In addition, NiSi has another advantage capable ofdecreasing a process temperature because it can be formed at a lowertemperature than that of TiSi₂ and CoSi₂. Accordingly, NiSi has beensupposed to be promising as a future contact material.

FIG. 1A to FIG. 1B are partial traverse cross sectional views showing asilicon substrate at each process according to a conventional generalformation method of metal silicides. On silicon substrate 51, region 57is formed, where a dopant concentration is high by, for example, ionimplantation. This region 57 corresponds to a source/drain region of aMOS transistor. For forming a metal silicide, as shown in FIG. 1A,first, for example, metal film 52 such as titanium or cobalt isdeposited on silicon substrate 51, on which region 57 is formed using,for example, a sputtering method or a molecular beam epitaxy. Next, ametal atom in metal film 52 and a silicon atom of substrate 51 arereacted by annealing the substrate at an appropriate temperature.Through the above-described formation method, metal silicide film 55shown in FIG. 1B is formed.

Also, a MOS transistor using a metal silicide has been conventionallyfabricated with a process called a salicide process. FIG. 2A to FIG. 2Dare partial traverse cross sectional views showing a MOS transistor ateach process according to a conventional salicide process. First, inFIG. 2A, device isolation region 152, gate insulator film 153, gateelectrode 154, gate sidewall 155, source/drain region 156 are formed onsilicon substrate 151 using general fabrication processes of a MOStransistor. Device isolation region 152 and gate sidewall 155 are formedwith an insulator such as silicon oxide or silicon nitride, and polysilicon is used for gate electrode 154. In addition, source/drain region156 is formed by ion implanting dopant impurities such as boron andarsenic into silicon substrate 151, and then conducting an activationanneal after that.

Next, as shown in FIG. 2B, metal film 157 such as cobalt and nickel, isdeposited on a whole surface of the substrate using, for example, aspattering method.

After that, by annealing the substrate at an appropriate temperature, ametal of the deposited metal film 157, and silicon of source/drainregion 156 and gate electrode 154 are reacted to form metal silicidefilm 158 in FIG. 2C. In this case, since the metal atoms react only at aplace where a single crystal silicon of source/drain region 156 or apoly crystal silicon of gate electrode 154 is exposed, the metal atomson device isolation region 152 and gate sidewall 155 remain as metalfilm 159 without reaction.

Then, by removing the unreacted metal film 159 using an appropriateetching solution, for example, a mixed solution of sulfuric acid andhydrogen peroxide, metal silicide film 158 can be formed only onsource/drain region 156 and gate electrode 154 as shown in FIG. 2D.

As described in the above, according to the conventional metal silicideformation method, silicon atoms in the substrate or the gate electrodeare reacted with metal atoms deposited on them.

Recently, on the other hand, for increasing a performance of a MOStransistor, there is a tendency for further thinning a source/drainregion. In a silicon MOS transistor, the junction leak characteristicbecomes poor as the formed metal silicide approaches to a p-n junctionof the source/drain, and if the contact penetrates the source/drain, thetransistor does not operate correctly. Therefore, the metal silicidefilm must be shallower than the source/drain region as shown in FIG. 1B.Since the metal silicide film is formed through a reaction of siliconatoms at source/drain region and metal atoms, the metal silicide film ofthe contact is also further thinned with a thinning of the source/drainregion. However, if the metal silicide film is thinned, a sheetresistance of the metal silicide film increases, thereby resulting indecrease of the performance of the MOS transistor. In addition, if athickness of the silicide film is increased, a leakage current increasesdue to approaching of the formed metal silicide film to the p-n junctionat the source/drain region, thereby resulting in substantial decrease intransistor performance.

A ratio b/a of a film thickness a of the formed metal silicide to a filmthickness b of silicon consumed through a silicide reaction is called asa silicon consumption factor. A value of this consumption factor isdifferent by a kind of metal. Since a consumption factor value of NiSiis small, NiSi has an advantage for thinning die source/drain region.However, it also consumes silicon atoms of the substrate, then, thethinning is limited. Therefore, other method for forming a metalsilicide film which consumes less silicon atoms of the substrate, aswell as progressing further miniaturization of a transistor, isrequired.

As one of such a metal silicide formation method, a method in which anickel silicide (NiSi₂) is grown with epitaxy by a thermal treatmentafter alternately depositing Ni and Si on a Si substrate has beendisclosed in Japanese Laid-open Patent publication No 61-212017. Also, amethod for forming NiSi has been disclosed in Japanese Laid-open Patentpublication No 8-97420 by conducting a thermal treatment afterdepositing Ni on silicon to form Ni2Si, and after that, another thermaltreatment is conducted again after depositing a poly silicon film on theNi2Si to form the NiSi. In addition, a method for forming NiSi has beendisclosed in U.S. Pat. No. 4,663,191 by depositing Ni and Sisimultaneously.

In the conventional methods for forming metal silicide by reacting themetal in a metal film with the substrate silicon as exemplified in theabove, when the source/drain region is thinned, it is impossible toobtain a sufficient film thickness of nickel silicide, even if nickelsilicide is used, which has a small consumption factor, therebyresulting in substantial consumption of silicon atoms of the substratesilicon. Therefore, a method for forming nickel silicide having smallsilicon atom consumption of the silicon substrate has been required

However, if the method disclosed in Japanese Laid-open Patentpublication No 61-212017 is used, a silicide having nickel disilicide(NiSi₂) is formed as a main composition rather than nickel monosilicide(NiSi). Since the NiSi2 has a high resistivity, this is not suitable fora contact material. In addition, if the method disclosed in JapaneseLaid-open Patent publication No 8-97420 is used, nickel is reacted firstwith silicon substrate to form NiSi₂, then, substantial substratesilicon is consumed in this process. Therefore, there is a limitationfor increasing the thickness of NiSi. Also, due to use of salicideprocess, the above process becomes to be extremely complex. Further,although a salicide process is available for the method disclosed inU.S. Pat. No. 4,663,191, a control of composition ratio between Ni andSi is difficult because of simultaneous deposition of nickel andsilicon, and the final product of NiSi2 has a high resistivity, therebyresulting in unsuitable material for the contact material.

As described in the above, it has been difficult to realize a salicideprocess which is able to form a nickel silicide having a sufficientthickness and a low resistivity, while silicon consumption in siliconsubstrate is small enough.

DISCLOSURE OF THE INVENTION

The present invention has been developed for solving the above issues.

It is therefore a first object of the present invention to provide amethod for forming a nickel silicide film having a sufficient thicknessand a low resistivity, while silicon consumption in silicon substrate issmall enough.

It is a second object of the present invention to provide a fabricationmethod of a semiconductor device using the method for forming the nickelsilicide film.

It is a third object of the present invention to provide an etchingmethod of the nickel silicide film which uses a difference of etchingcharacteristic of the nickel silicide film according to a compositionratio of Ni and Si in the film.

According to the first aspect of the present invention for achieving thefirst object in the above, the present invention provides a nickelsilicide film formation method comprising the steps of: a step forforming a stacked layer film by alternately forming at least one nickellayer and at least one silicon layer of an amorphous state on asubstrate at a first substrate temperature which does not cause asilicide reaction; and a step of the silicide reaction for formingnickel monosilicide by implementing a thermal treatment of the stackedlayer film at a second substrate temperature which causes a nickelmonosilicide reaction, wherein, in the step for forming the stackedlayer film, a ratio (N_(Ni)/N_(si)) of the number of total nickel atoms(N_(Ni)) to the number of total silicon atoms (N_(si)) existing in awhole stacked layer film is equal to or more than 1.

In the fist aspect of the present invention, since a silicon layer and anickel layer are alternately formed at least one layer for the each at asubstrate temperature which does not cause the silicide reaction, theformed silicon layer is an amorphous state. Nickel atoms preferentiallydiffuse into an amorphous layer rather than a single crystal siliconlayer and a poly crystal silicon layer. Therefore, in the later silicidereaction process, nickel atoms preferentially diffuse into silicon ofthe amorphous silicon layer to form a nickel silicide film. In addition,since the silicide reaction process is implemented at a temperature toform nickel monosilicide, a formation of nickel disilicide, which has ahigh resistivity, can be suppressed, and nickel monosilicide having alow resistivity can stably be formed. Further, since the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is equal to or more than 1, excess silicon atoms necessaryfor forming nickel disilicide do not exist in the amorphous, siliconlayer where nickel atoms preferentially diffuse into, thereby resultingin stably formation of nickel monosilicide, which has a low resistivity.Also, since the silicon layer and the nickel layer are alternatelydeposited at least one layer for the each, nickel monosilicide having alow resistivity with sufficient thickness can be formed, whilesuppressing silicon atom consumption consumed for the silicide reactionby adjusting each thickness and number of layers of the silicon layerand the nickel layer.

In the process for forming the stacked layer film, it is favorable toform the stacked layer film so that a ratio of the number of nickelatoms in each nickel layer to the number of silicon atoms in eachsilicon layer is equal to a ratio of the number of total nickel atoms tothe number of total silicon atoms existing in the whole stacked layerfilm. According to this invention, since the ratio of the number ofnickel atoms to the number of silicon atoms in the nickel layer and thesilicon layer, which are alternately deposited, is set equal to theratio of the number of total nickel atoms to the number of total siliconatoms existing in the whole stacked layer film, a uniform nickelmonosilicide can be formed through uniform nickel diffusion into thewhole stacked layer film during the silicide reaction. As a result,nickel monosilicide, which has a low resistivity, can stably be formed.

In addition, in the stacked layer film formation process, it isfavorable to form the stacked layer film so that the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in whole stacked layerfilm is equal to or more than 1, and equal to or less than 4. Accordingto this invention, a nickel silicide film which is able to suppresssilicon atom consumption of the substrate compared with a conventionalmethod can be formed.

Further, it is favorable that the nickel silicide contains the nickelmonosilicide equal to or more than 50%. According to this invention, theformed nickel silicide film is preferably applied to the contact of aMOS transistor.

Furthermore, the above-described present invention can be applied to thecase where the substrate includes one or more regions of semiconductorsselected from a group of single crystal silicon, poly crystal silicon,distorted silicon, single crystal silicon-germanium, poly crystalsilicon-germanium, and distorted silicon-germanium at an uppermostsurface of the substrate.

According to this invention, since a nickel silicide film is formedthrough a reaction of nickel and silicon, it is possible to apply thisinvention to a substrate surface, where the nickel silicide film isformed, other than silicon, for example, single crystalsilicon-germanium, poly crystal silicon-germanium, and distortedsilicon-germanium. If nickel deposited on silicon-germanium mixedcrystal is thermally treated, nickel germanosilicide Ni(Si_(1-x)Ge_(x))is formed. The Ni(Si_(1-x)Ge_(x)) has a higher resistivity than NiSi.Then, according to this invention, a film having a lower resistivity canbe obtained than the case where silicon-germanium mixed crystal andnickel are reacted. Therefore, it is also possible to increase atransistor performance if silicon-germanium mixed crystal is used forthe source/drain region and poly crystal silicon-germanium is used forthe gate electrode of a MOS transistor.

In addition, the substrate may be one selected from a group of a siliconsubstrate, a SOI substrate, and a SGOI substrate. According to thisinvention, by applying this invention to a silicon on insulator (SOI)substrate and a silicon-germanium on insulator (SGOI) substrate as wellas the silicon substrate, an advantage which prevents from degrading aMOS transistor performance due to reaching of the nickel silicide filmto a buried oxide film can be obtained.

According to the second aspect of the present invention for achievingthe second object in the above, the present invention provides asemiconductor device fabrication method comprising steps of: a step forforming a stacked layer film by alternately forming at least one nickellayer and at least on silicon layer of an amorphous state on at leastone semiconductor region and on at least one insulator region on asubstrate at a first substrate temperature which does not cause asilicide reaction; a step of the silicide reaction for forming a nickelsilicide film containing nickel monosilicide, of which composition isdifferent on the semiconductor region and on the insulator region, byimplementing a thermal treatment of the stacked layer film at a secondsubstrate temperature which causes a nickel monosilicide reaction; andan etching step for removing the nickel silicide film on at least oneinsulator region by etching, wherein, in the step for forming thestacked layer film, a ratio (N_(Ni)/N_(si)) of the number of totalnickel atoms (N_(Ni)) to the number of total silicon atoms (N_(si))existing in the whole stacked layer film is equal to or more than 1.

The second aspect of the present invention is a semiconductor devicefabrication method using a nickel silicide film according to the firstaspect of the present invention. The effects and advantages are similarto the aboves. According to the second aspect of the present invention,the ratio (N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni))to the number of total silicon atoms (N_(si)) existing in the wholestacked layer film is equal to or more than 1. A typical semiconductorregion where silicon is exposed includes a source/drain region and agate electrode, but not limited to these. A typical insulator regionincludes a silicon oxide region and a silicon nitride region, but alsonot limited to these. In the semiconductor region, since excess nickelatoms in the stacked layer film diffuse into the semiconductor regionduring the silicide reaction, nickel monosilicide is formed at theinterface between the stacked layer film and the semiconductor region.On the other hand, in the insulator region, since the excess nickelatoms in the stacked layer film are bard to diffuse, nickel-rich nickelsilicide is formed at the interface between the stacked layer film andthe insulator region. When the stacked layer film uniformly formed onthe semiconductor region and the insulator region is caused the silicidereaction, a composition of the nickel silicide after the silicidereaction changes like the above-described according to a kind of thebase of the stacked layer film. Especially, the nickel-rich nickelsilicide is easily etched. On the other hand, the nickel monosilicide ishard to etch. The inventor have found this fact and resulted ininvention of the present invention. Therefore, according to the presentinvention, by etching the uniformly formed stacked layer film after thesilicide reaction, the nickel silicide film on the insulator, which isnickel-rich, is selectively etched. Then, a fabrication efficiency of asemiconductor device having a nickel monosilicide film can be increased.

In the semiconductor fabrication method of the present invention, it isfavorable that the nickel silicide on the semiconductor region and onthe insulator region after the silicide reaction becomes nickelmonosilicide and nickel-rich nickel silicide, respectively.

According to this invention, it is possible to cause the silicidereaction to the uniformly formed slacked layer film, and after that, toselectively etch only the nickel silicide film on the insulator.

In addition, in the semiconductor fabrication method of the presentinvention, it is favorable that the semiconductor region includes one ormore semiconductors selected from a group of single crystal silicon,poly crystal silicon, distorted silicon, single crystalsilicon-germanium, poly crystal silicon-germanium, and distortedsilicon-germanium, and it is also favorable that the insulator region issilicon oxide and/or silicon nitride, and, further, it is favorable thatthe substrate is any one selected from a group of a silicon substrate, aSOI substrate, and a SGOI substrate.

According to this invention, the invention can be applied to forming acontact of a usual MOS transistor which is configured, for example, suchthat the source/drain layer is single crystal silicon, the gateelectrode is poly crystal silicon, and the gate sidewall and deviceisolation region are silicon oxide or silicon nitride. In addition, byapplying the invention to a SOI substrate and a SOI substrate other thana silicon substrate, it is possible to prevent from degrading MOStransistor performance due to reaching of the nickel silicide film tothe buried oxide layer.

According to the third aspect of the present invention for achieving thethird object in the above, the present invention provides an etchingmethod for etching a nickel-rich region located on an insulator regionof a nickel silicide film which is formed on at least one semiconductorregion and on at least one insulator region on a substratc and acomposition of the nickel silicide film is different between thesemiconductor region and the insulator region, wherein a ratio(N_(Ni)/N_(si)) of the number of nickel atoms (N_(Ni)) to the number ofsilicon atoms (N_(si)) in the nickel-rich region is equal to or morethan 1.11.

According to the fourth aspect of the present invention for achievingthe third object in the above, the present invention provides anetching, method for etching a nickel-rich region located on an insulatorregion of a nickel silicide film which is formed on at least onesemiconductor region and at least one insulator region on a substrateand a composition of the nickel silicide film is different between thesemiconductor region and the insulator region, wherein the nickel-richregion has a diffraction peak of Ni₂Si in X-ray diffraction pattern.

According to the fifth aspect of the present invention for achieving thefirst object in the above, the present invention provides a nickelsilicide formation method comprising steps of: a step for forming alayer structure containing silicon and nickel on at least onesemiconductor region and on at least one insulator region on asubstrate; and a step of silicide reaction for forming a nickel silicidefilm of which composition is different on the semiconductor region andthe insulator region such that the composition on the insulator regionis nickel-rich by implementing a thermal treatment of the layerstructure at a second substrate temperature which causes a silicidereaction, wherein, in a nickel-rich region located on the insulatorregion of the nickel silicide film, a ratio (N_(Ni)/N_(si)) of thenumber of nickel atoms (N_(Ni)) to the number of silicon atoms (N_(si))is equal to or more than 1.11.

According to the sixth aspect of the present invention for achieving thefirst object in the above, the present invention provides a nickelsilicide formation method comprising steps of: a step for forming alayer structure containing silicon and nickel on at least onesemiconductor region and on at least one insulator region on asubstrate; and a step of a silicide reaction for forming a nickelsilicide film of which composition is different on the semiconductorregion and the insulator region so that the composition on the insulatorregion is nickel-rich by implementing a thermal treatment of the layerstructure at a second substrate temperature which causes a silicidereaction, wherein a nickel-rich region located on the insulator regionof the nickel silicide film has a diffraction peak of Ni₂Si in X-raydiffraction pattern.

According to the third to the sixth aspects of the present invention, inthe case of (1) the ratio (N_(Ni)/N_(si)) of the number of nickel atoms(N_(Ni)) to the number of silicon atoms (N_(si)) is equal to or morethan 1.11, or (2) the nickel silicide film has a diffraction peak ofNi₂Si in X-ray diffraction pattern, the nickel silicide is nickel-richnickel silicide. The inventors of the present invention have found thatnickel-rich nickel silicide is easily etched, and that, nickelmonosilicide is hard to etch, thereby resulting in invention of thepresent invention. Therefore, according to the present invention, sinceonly nickel-rich region on the insulator region of the nickel silicidefilm can selectively be etched, an efficient etching process can berealized.

In the third to the sixth aspects of the present invention, a region ofnickel silicide film located on the semiconductor region is composed ofnickel monosilicide, and a region of nickel silicide film located on theinsulator region is composed of nickel-rich nickel silicide.

In addition, in the third to the sixth aspects of the present invention,it is favorable that the semiconductor region includes one or moresemiconductors selected from a group of single crystal silicon, polycrystal silicon, distorted silicon, single crystal silicon-germanium,poly crystal silicon-germanium, and distorted silicon-germanium, and itis also favorable that the insulator region is silicon oxide and/orsilicon nitride.

In addition, in the third to the sixth aspects of the present invention,a nickel monosilicide film can selectively be formed only on variouskinds of silicon semiconductors. In addition, for example, this can beapplied to a distorted channel MOS transistor which is fabricated on adistorted silicon or a distorted silicon-germanium only on which asilicide contact can be formed efficiently. As a result, by suppressingrelaxation of the distortion around the channel region, it is possibleto prevent from decreasing performance of the distorted channel MOStransistor, and to sufficiently extract original performance of thedistorted channel MOS transistor.

In addition, in the third to the sixth aspects of the present invention,it is favorable that the nickel silicide film is formed by causing thesilicide reaction after alternately depositing nickel and silicon, orafter co-depositing nickel and silicon.

According to the present invention, a nickel silicide film, which is tobe selectively etched, may be a silicide reacted after formingmulti-stacked layers, or may be a silicide reacted after co-depositionof nickel and silicon. The etching method of the present invention is,in any cases, can selectively etch only nickel-rich nickel silicide.

Furthermore, it is favorable that the substrate is any one selected froma group of a silicon substrate, a SOI substrate, and a SGOI substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 1B are partial traverse cross sectional views showing asilicon substrate at each process according to a conventional generalformation method of metal silicides.

FIG. 2A to FIG. 2D are partial traverse cross sectional views showing aMOS transistor at each process according to a conventional salicideprocess.

FIG. 3A to FIG. 3B are partial traverse cross sectional views showing asubstrate at each step relating to formation of a nickel silicide filmhaving nickel monosilicide as a main composition on a silicon substrate.

FIG. 4A and FIG. 4B are, in the second embodiment of the presentinvention, partial traverse cross sectional views showing a substrate ateach process relating to a method for forming a nickel silicide filmcontaining nickel monosilicide as a main composition on a siliconsubstrate.

FIG. 5A to FIG. 5E are, in the third embodiment of the presentinvention, partial traverse cross sectional views showing each processrelating to a method of nickel silicide film formation when a nickelsilicide film is applied to a contact of the source/drain and the gateelectrode.

FIG. 6 is a figure showing an example of X-ray diffraction pattern of anickel silicide film which is formed on Si and SiO₂.

FIG. 7 is a cross sectional TEM photograph of Ni₂Si formed on SiO₂before etching.

FIG. 8 is a cross sectional TEM photograph of Ni₂Si formed on SiO₂ afteretching.

FIG. 9A to FIG. 9D are partial traverse cross sectional views showingeach process according to one example of method of the fourth embodimentof the present invention for forming a nickel silicide film containingnickel monosilicide as a main composition on a source/drain region and agate electrode of a MOS transistor on a silicon substrate with aself-aligning manner.

FIG. 10 is a partial enlarged traverse cross sectional view of a MOStransistor shown in FIG. 9B.

FIG. 11A to FIG. 11B are partial traverse cross sectional views showingeach process according to one example of method of the fifth embodimentof the present invention for forming a nickel silicide film containingnickel monosilicide as a main composition on a source/drain region and agate electrode of a MOS transistor on a silicon substrate with aself-aligning manner.

FIG. 12 is a partial traverse cross sectional view showing a MOStransistor on a SOI substrate, which is formed a nickel silicide filmusing the sixth embodiment of the present invention with a methodsimilar to that of the above-described fourth and fifth embodiments.

FIG. 13 is a partial traverse cross sectional view showing a MOStransistor formed on a distorted silicon layer using the seventhembodiment of the present invention with a method similar to that of theabove-described fourth to sixth embodiments.

FIG. 14A to FIG. 14D are partial traverse cross sectional views showingeach process according to one example of method of the eighth embodimentof the present invention for forming a nickel silicide film containingnickel monosilicide as a main composition on a source/drain region and agate electrode of a MOS transistor on a silicon substrate with aself-aligning manner.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

Embodiments of the present invention will be explained by referring tofigures.

(A Nickel Silicide Film Formation Method)

According to a nickel silicide film formation method of the presentinvention, the method comprises a step for forming a stacked layer filmby alternately stacking at least one nickel layer and at least onesilicon layer of an amorphous state on a substrate at a first substratetemperature which does not cause a silicide reaction, and a step of thesilicide reaction for forming nickel monosilicide by implementing athermal treatment of the stacked layer film at a second substratetemperature which causes a nickel monosilicide reaction, wherein, in thestep for forming the stacked layer film, a ratio (N_(Ni)/N_(si)) of thenumber of total nickel atoms (N_(Ni)) to the number of total siliconatoms (N_(si)) in the whole stacked layer film being equal to or morethan 1 is important.

First Embodiment

A nickel silicide film formation method in a first embodiment of thepresent invention will be explained.

FIG. 3A to FIG. 3B are partial traverse cross sectional views showing asubstrate at each step relating to formation of a nickel silicide filmhaving nickel monosilicide as a main composition on a silicon substrate.

In the present invention, nickel silicide film 15 means a nickelsilicide film having nickel monosilicide as a main composition.Meanwhile, an example of composition other then the main composition is,for example, nickel atoms, silicon atoms, and nickel disilicide, whichare existing in the film without the silicide reaction. Especially, itis favorable that the nickel monosilicide is contained in the nickelsilicide film more than 50%, more favorable if the nickel monosilicideis more than 80%, and the most favorable if the nickel monosilicide ismore than 90%. The higher the ratio of nickel monosilicide in the nickelsilicide film is, the better the film is for a contact material of a MOStransistor. In the present invention, a “main composition” is used as aword for meaning existence of more than 50% of nickel monosilicide inthe film.

Regarding silicon substrate 11, it is no matter whether the siliconsubstrate is single crystal silicon or poly crystal silicon. However, asfor the surface orientation, other than a (111) surface, for example, a(100) surface or a slightly declined (100) surface is favorable for aprincipal surface. The reason is that an epitaxial growth issue ofnickel disilicide easily takes place if the (111) surface is employed asthe principal surface.

On a surface of silicon substrate 11, a high dopant concentration layermay be formed using ion implantation and with an activation thermaltreatment. Also, one or more semiconductor regions selected from a groupof distorted silicon, single crystal silicon-germanium, poly crystalsilicon-germanium, and distorted silicon-germanium may be included onthe uppermost surface of the substrate.

According to the nickel silicide film formation method of the presentinvention, nickel layer 12 and silicon layer 13 are alternately formedon silicon substrate 11 at the beginning. In FIG. 3A, nickel layer 12,silicon layer 13, nickel layer 12, silicon layer 13, and so on, aredeposited in order three layers in total for the each from a side closeto silicon substrate 11. Nickel layer 12 and silicon layer 13 are formedby depositing nickel atoms and silicon atoms using optionally, forexample, a sputtering method and a molecular beam epitaxy method,respectively

A first substrate temperature, which is a temperature of siliconsubstrate 11, for forming nickel layer 12 and silicon layer 13 is set ata temperature which does not cause a silicide reaction between thedeposited nickel layer 12 and silicon layer 13. Since nickel layer 12and silicon layer 13 are alternately deposited on a substrate of whichtemperature is set at the first substrate temperature, the silicidereaction between nickel atoms and silicon atoms does not take place, andin addition, silicon layer 13 can be formed with an amorphous state. Thefirst substrate temperature may arbitrarily be changed by consideringdeposition conditions, for example, a kind of deposition apparatus to beused and thicknesses of nickel layer and silicon layer. However,regarding a range of the temperature, it is favorable that the range isabout 20° C. at room temperature to 200° C. in general, and 50° C.-100°C. is more preferable. The lowest temperature of the range is decidedmainly from view point of preventing from adsorbing impurities on thesubstrate surface from atmosphere.

In the present invention, thicknesses of nickel layer 12 and siliconlayer 13 are set such that a ratio (N_(Ni)/N_(si)) of the number ofnickel atoms (N_(Ni)) to the number of silicon atoms (N_(si)) in thewhole stacked layer film is equal to or more than 1. That is, thethickness of nickel layer 12 and that of silicon layer 13 are set suchthat a ratio (N_(Ni):N_(si)) of the number of total nickel atoms to thenumber of total silicon atoms existing in the whole stacked layer filmis 1:1, or nickel is more than silicon. For example, if the ratio iscalculated using atomic mass and specific gravity of nickel and silicon,the ratio (N_(Ni):N_(si)) of the number of total nickel atoms (N_(Ni))to the number of total silicon atoms (N_(si)) existing in the wholestacked layer film becomes 1:1 when a ratio of the total thickness ofthe nickel layer to the total thickness of the silicon layer in thewhole stacked layer is 1.79. Therefore, 1 or more of the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film can be achieved by making that the ratio of the totalthickness of silicon layer to the total thickness of nickel layer in thewhole stacked layer is 1.79 or less.

By using the stacked layer film in which the ratio (N_(Ni):N_(si)) ofthe number of total nickel atoms to the number of total silicon atoms iscontrolled to be 1:1, a nickel silicide film containing nickelmonosilicide as a main composition, which is uniform and wellcrystallized, can be formed through complete reaction of nickel atoms inthe stacked nickel layer and silicon atoms in the silicon layer with asilicide reaction process which will be described later.

In addition, in the stacked layer film in which the ratio(N_(Ni):N_(si)) of the number of total nickel atoms to the number oftotal silicon atoms is controlled to be 1:1, or nickel is more thansilicon, there exist excess nickel atoms which were not reacted withsilicon atoms in the silicon layer, and the excess nickel atoms reactwith silicon atoms in the substrate by diffusing into the substrate.However, the excess nickel atoms reacting with silicon atoms in thesubstrate are the atoms which were not reacted with the stacked siliconlayer 13, and the quantity is bit. Therefore, a nickel silicide filmcontaining nickel monosilicide as a main composition, which is uniformand well crystallized, can be formed. By changing thicknesses of nickellayer 12 and silicon layer 13 which are alternately stacked, a thicknessof nickel silicide to be formed can also be changed. On the other hand,when the number of silicon atoms in stacked silicon layer 13 is largerthan that of nickel atoms in nickel layer 12, excess silicon atoms mayremain to be unreacted, and nickel disilicide having a high resistivitymay also be formed. As a result, the obtained nickel silicide filmbecomes not uniform and not well crystallized, and its resistivitybecomes high.

If the ratio (N_(Ni)/N_(si)) of the number of total nickel atoms(N_(Ni)) to the number of total silicon atoms (N_(si)) in the wholestacked layer film is much larger than 1, the excess nickel atoms whichhave not reacted with silicon atoms in the stacked silicon layer reactwith silicon in the substrate by diffusing into the substrate.Therefore, it is favorable that the ratio (N_(Ni)/N_(si)) of the numberof total nickel atoms (N_(Ni)) to the number of total silicon atoms(N_(si)) in the whole stacked layer film is not increased too much forthe purpose of the present invention which intends to reduce siliconconsumption in the substrate as much as possible.

For considering a favorable range of the ratio (N_(Ni)/N_(si)) of thenumber of total nickel atoms (N_(Ni)) to the number of total siliconatoms (N_(si)) in the whole stacked layer film, for example, a case forforming a nickel silicide film of 10 nm in thickness on the substratewill be examined. A consumption factor of nickel silicide containingnickel monosilicide as a main composition, that is, a ratio (b/a) of athickness b of silicon consumed by the silicide reaction to a thickness;a of formed nickel silicide film is about 0.82. Then, according to theconventional method shown in FIG. 1A and FIG. 1B, a silicon of about 8nm in thickness in upper region of the silicon substrate is consumed. Onthe contrary, according to the embodiment of the present invention shownin FIG. 3A and FIG. 3B, most of nickel atoms in the deposited nickellayer and most of silicon atoms in the deposited silicon layer reactcompletely to form nickel monosilicide. As a result, a quantity ofsilicon consumption (referred to as symbol b in FIG. 3B) in the siliconsubstrate is about 4 nm in thickness in upper region of the siliconsubstrate when the number of total nickel atoms (N_(Ni)):the number oftotal silicon atoms (N_(si))=2:1, and about 6 nm in thickness in upperregion of the silicon substrate when the number of total nickel atoms(N_(Ni)):the number of total silicon atoms (N_(si))=4:1, and also about7 nm in thickness in upper region of the silicon substrate when thenumber of total nickel atoms (N_(Ni)):the number of total silicon atoms(N_(si))=5:1. Therefore, if improvement of at least 25% is requiredcompared with the conventional method shown in FIG. 1A and FIG. 1B, itis favorable that the ratio (N_(Ni)/N_(si)) of the number of totalnickel atoms (N_(Ni)) to the number of total silicon atoms (N_(si))existing in the whole stacked layer film is equal to or more than 1, andequal to or less than 4.

In addition, if a region of silicon-germanium mixed crystal layer or aregion of poly crystal silicon-germanium layer is included in theuppermost of the substrate surface, it is favorable to form nickelmonosilicide by adjusting condition so that a part of nickel atoms inthe deposited nickel layer on the substrate reacts with silicon in thesubstrate. For the above condition, as with the case described in theabove for forming nickel silicide film on the silicon substrate, it isfavorable that the ratio (N_(Ni)/N_(si)) of the number of total nickelatoms (N_(Ni)) to the number of total silicon atoms (N_(si)) existing inthe whole stacked layer film is 1 to 4 by considering the consumptionfactor.

Through the reaction of the part of nickel atoms in the nickel layerwith silicon atoms in the substrate, it is possible to reflect acrystallity of single crystal silicon in the substrate to a crystallityof the formed nickel monosilicide. As a result, a nickel monosilicidefilm with better crystallity can be obtained. In addition, when a baseof the stacked layer film is a silicon layer or a silicon-germaniumlayer, it is possible to reduce a contact resistance by consumingsilicon atoms in the base. To obtain this effect, it is favorable toincrease nickel atoms more than that the ratio (N_(Ni)/N_(si)) of thenumber of total nickel atoms (N_(Ni)) to the number of total siliconatoms (N_(si)) existing in the whole stacked layer film is 1:1. That is,it is favorable to configure that the ratio (N_(Ni)/N_(si)) of thenumber of total nickel atoms (N_(Ni)) to the number of total siliconatoms (N_(si)) existing in the whole stacked layer film is equal to ormore than 1, and equal to or less than 4.

Further, for example, regarding a MOS transistor, a thickness of asource drain layer is becoming thinner with progress of theminiaturization. In this case, it is favorable that the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is equal to or less than 4. If a consumption factor of 0.61is required, it can be achieved by configuring that the ratio,(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is equal to or less than 3, and if the consumption factor of0.41 is required, it can be achieved by configuring that the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is equal to or less than 2. Also, considering furtherminiaturization in a future, it is favorable to configure that the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is equal to or less than 2.

In these stacked layer film formation process, it is favorable that aratio of the number of nickel atoms (N_(Ni)) in each nickel layer to thenumber of silicon atoms (N_(si)) in each silicon layer is equal to theratio (N_(Ni/)N_(si)) of the number of total nickel atoms (N_(Ni)) tothe number of total silicon atoms (N_(si)) existing in the whole stackedlayer film. To make the ratios equal between the atoms in each layer andthat of in the whole stacked layer film is, for example, to configurethat a ratio of the number of nickel atoms (N_(Ni)) in one nickel layerto the number of silicon atoms (N_(si)) in one silicon layer is equal tothe ratio of the number of total nickel atoms (N_(Ni)) to the number oftotal silicon atoms (N_(si)) existing in the whole multi-stacked layerfilm.

By making the configuration like these, a diffusion of nickel during asilicide reaction, which will be described later, is uniformly performedat each portion of the stacked layer film, thereby resulting in easyformation of uniform nickel monosilicide. Accordingly, it becomespossible to stably form a nickel monosilicide having a low resistivity.

In the present invention, it is important that the number of nickelatoms and the number of silicon atoms in the stacked layer film have arelation described in the above, and the film is formed with a conditionwithin the range of the relation. A thickness of a practically formedeach nickel layer or silicon layer is in a range of 2 nm˜10 nm ingeneral. For stimulating the silicide reaction by rapidly diffusingnickel atoms into silicon, it is favorable to thin the nickel layer asthin as possible. However, since nickel disilicide is likely to beformed and a long time is needed for the stacking process due to manystacking layers when the nickel layer is too thin, it is favorable thatthe thickness is set within the above range. The number of stackinglayers is decided considering a thickness of a final nickel silicidefilm to be obtained, that is, a nickel silicide film of 10˜30 nm inthickness is formed in general considering the number of each nickellayer and silicon layer based on each thickness of the layers.

Next, a silicide reaction process will be explained. A nickel silicidefilm formation method of the present invention is, as described in theabove, performed by implementing a thermal treatment at a secondsubstrate temperature which causes a nickel monosilicide formation. As aresult, as shown in FIG. 3B, nickel silicide film 15 containing nickelmonosilicide as a main composition is obtained. Regarding the method ofthe thermal treatment, for example, annealing with a common furnace or arapid thermal anneal (ETA) can be optionally used. As for the secondsubstrate temperature, any temperature can be selected if the nickelmonosilicide is stably formed at the temperature. The second substratetemperature is, although it is modified according to a method of thethermal treatment, preferably within a range of 300° C.˜750° C. ingeneral, and 350° C.˜500° C. is more preferable. When the secondsubstrate temperature is higher than 750° C., a nickel silicide filmcontaining nickel disilicide, which has a high resistivity, as a maincomposition is formed. On the other hand, when the second substratetemperature is lower than 300° C., nickel monosilicide is not alwaysformed due to insufficient silicide reaction.

A preliminary thermal treatment at a low temperature before the thermaltreatment at the second substrate temperature may be conducted. In thiscase, it is favorable that a temperature of the preliminary thermaltreatment at a low temperature is lower than the second substratetemperature. If a high temperature is used for the thermal treatment atthe beginning, an abnormal high temperature may locally appear, therebyresulting in possibility to cause variations of, such as, a compositionand a film thickness of the nickel silicide film. Through thepreliminary thermal treatment at a low temperature, a change ofcrystallity of the nickel layer and the silicon layer composing thestacked layer film is caused without completing the silicide reaction.That is, the nickel layer and the silicon layer are changed fromamorphous states to more crystalline states. Conducting the thermaltreatment at the second substrate temperature after that, a gradient oftemperature rise is reduced, as a result, it becomes possible to stablyform the nickel silicide film without causing variations of such as thecomposition and the film thickness.

Regarding an atmosphere during the thermal treatment, vacuum orarbitrary gas atmosphere, for example, gas atmosphere such as nitrogenmay be used. However, it is favorable that the atmosphere does notcontain oxygen as possible as it can for not to oxidize the stackednickel layer and the silicon layer. In addition, a time for the thermaltreatment is decided considering a total thickness of the stacked layerfilm, a method of the thermal treatment, and a temperature of thethermal treatment. The time is 5˜60 minutes for the thermal treatmentwith a common furnace, and 10˜120 seconds for the RTA.

By conducting the above thermal treatment, nickel monosilicide is formedthrough a reaction of nickel atoms in nickel layer 12 with silicon atomsby diffusing the nickel atoms into silicon layer 13. In this process, apart of nickel atoms in nickel layer 12 nearest to substrate 11 alsodiffuses into silicon substrate 11. However, since the upper siliconlayer 13 adjacent to nickel layer 12 is made of amorphous silicon ascontrasted with crystal silicon of silicon substrate 11, nickel atomspreferentially diffuse into the upper amorphous silicon to form nickelmonosilicide.

In addition, by forming a stacked layer film such that a ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is 1:1 or nickel is more than silicon, nickel atoms are lefteven if silicon atoms in silicon layer 13 are completely changed intonickel monosilicide. The extra nickel atoms also form nickelmonosilicide by diffusing into silicon substrate 11, thereby reactingwith silicon in the substrate.

Accordingly, in the present embodiment, as shown in FIG. 3B, a thicknessb which is the consumed thickness of silicon substrate 11 through thereaction can be made very small against a thickness a of the nickelsilicide film containing the formed nickel monosilicide as a maincomposition. Nickel silicide film 15 obtained through the above has agood uniformity and a good crystallity.

Furthermore, in the present embodiment, by reversing a stacking order ofthe nickel layer and the silicon layer, the silicon layer can be formedat a nearest layer to the substrate, next, the nickel layer on it, andthe next, the silicon layer, and so on in order. In the aboveconfiguration, nickel atoms in the nickel layer must pass through theamorphous silicon layer before reaching to the silicon substrate. As aresult, nickel monosilicide can be stably formed even if the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is just 1:1. In this case, it is possible to make the siliconconsumption of silicon substrate zero. However, by forming a stackedlayer film such that the ratio (N_(Ni)/N_(si)) of the number of totalnickel atoms (N_(Ni)) to the number of total silicon atoms (N_(si))existing in the whole stacked layer film is 1:1 or nickel is more thansilicon, thereby forming a nickel silicide film composed of nickelmonosilicide with a condition so that a part of nickel atoms react withsilicon in the silicon substrate, a better crystalline nickel silicidefilm can be obtained due to reflection of crystallity of single crystalsilicon in the substrate to the crystallity of the formed nickelmonosilicide.

As described before, according to the present embodiment, after forminga stacked layer film which stacks a nickel layer and a silicon layer, anickel silicide film is formed through a silicide reaction. However,instead of forming a stacked layer film, the nickel silicide film mayalso be formed by causing the silicide reaction after co-depositingnickel and silicon. In this case, a composition ratio. (N_(Ni)/N_(si))of the number of nickel and silicon atoms during the film formation isset, as described in the above, to be more than 1. The co-deposited filmthrough the above process is reacted through the silicide reaction byconducting a thermal treatment at the second substrate temperaturedescribed before. Regarding a co-deposition method of nickel andsilicon, various film formation methods such as a reactive spatteringmethod and a CVD method may be applied.

Meanwhile, regarding the crystal orientation of the substrate surface onwhich nickel silicide is formed, it has been already mentioned. A (100)surface or a slightly declined (100) surface is favorable for theorientation.

In addition, in the present embodiment, the substrate may be a siliconon insulator (SOI) substrate or a silicon-germanium on insulator (SGOI)substrate. In this case, when a MOS transistor is fabricated on a thinSOI or SGOI layer, degradation of the MOS transistor characteristicwhich is caused by reaching of the nickel silicide film, which containsnickel monosilicide as a main composition, to the buried oxide layer canbe prevented.

Second Embodiment

Next, a second embodiment of the instant application will be explained.FIG. 4A and FIG. 4B are, in the second embodiment of the presentinvention, partial traverse cross sectional views showing a substrate ateach process relating to a method for forming a nickel silicide filmcontaining nickel monosilicide as a main composition on a siliconsubstrate. The second embodiment is an example of a substrate in which asilicon-germanium mixed crystal layer 34 is formed on a surface ofsilicon substrate 31 in a nickel silicide formation method of thepresent invention.

As shown in FIG. 4A, as with the method of the first embodiment, nickellayer 32 and silicon layer 33 are alternately formed on thesilicon-germanium mixed crystal layer 34 at the beginning at a firstsubstrate temperature which does not cause silicide reaction. In thissecond embodiment, the first substrate temperature, at which nickellayer 32 and silicon layer 33 are formed, is set in a range of roomtemperature (about 20° C. in usual)˜200° C. which does not cause thesilicide reaction. As a result, silicon layer 33 becomes an amorphousstate, and also nickel, and silicon and silicon-germanium mixed crystaldo not react to each other during the deposition. In addition, as withthe first embodiment, it is favorable that the thicknesses of nickellayer 32 and silicon layer 33 are configured so that a ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film is 1:1, or nickel is more than silicon. A thickness of eachnickel layer 32 and each silicon layer 33, and the number of nickellayer 32 and silicon layer 33 are arranged considering a thickness ofnickel silicide film 35 to be formed.

Next, by implementing a thermal treatment at the second substratetemperature which mainly forms nickel monosilicide, as shown in FIG. 4B,nickel silicide film 35 containing nickel monosilicide as a maincomposition can be obtained. In this case, since a part of nickel atomsin nickel layer 32 diffuses into silicon-germanium mixed crystal layer34 and reacts with it, nickel germanosilicide (NiSi_(I-x)Ge_(x)) layer36 which has a high resistivity is formed between nickel silicide film35, which contains nickel monosilicide as a main composition, andsilicon-germanium mixed crystal layer 34. Therefore, according to thepresent embodiment, there is another advantage for obtaining a layerwhich has a lower resistivity than that obtained from the reactionbetween silicon-germanium mixed crystal and nickel. Then, the transistorperformance can be increased by using the silicon-germanium mixedcrystal in source/drain region of a MOS transistor in some case, and byforming the gate electrode with silicon-germanium mixed crystal in othercase.

Meanwhile, regarding the thermal treatment at the second substratetemperature, it is favorable that the thermal treatment is implementedin a temperature range of 300° C.˜750° C., and more favorably, 350° C.500° C., so as to form nickel monosilicide well and not to cause anickel disilicide reaction.

In the conventional thermal treatment method in which only nickel isdeposited, the all formed film become nickel germanosilicide, and it islikely to form defects at the interface between the nickelgermanosilicide layer and the silicon-germanium mixed crystal layer dueto germanium precipitation. However, in the present embodiment, it ispossible to extremely thin the nickel germanosilicide layer to be formedbecause nickel atoms easily diffuse into the amorphous silicon layer.For example, if a nickel silicide film of 10 nm in thickness is formedunder a condition that the ratio (N_(Ni)/N_(si)) of the number of totalnickel atoms (N_(Ni)) to the number of total silicon atoms (N_(si))existing in the whole stacked layer film is 2:1, the nickelgermanosilicide layer may be thinned to about 4 nm. Since a resistivityof nickel germanosilicide becomes higher with increase of germaniumconcentration, according to the present embodiment, a film having alower resistivity than that of the film formed with the conventionalmethod, where the thermal treatment is implemented after only nickeldeposition, can be obtained. In addition, during the thermal treatment,diffusion of germanium atoms in nickel germanosilicide layer takesplace. As a result, the germanium concentration in the nickelgermanosilicide layer becomes lower, resulting in further lowering ofthe resistivity.

Further, it is possible to form a silicon layer as a nearest layer tothe substrate by reversing the deposition order of the nickel layer andthe silicon layer. This is the same with the first embodiment.

In the present embodiment, a nickel silicide formation method of thepresent invention has been applied to the case where a silicon-germaniummixed crystal layer is formed on a surface of the silicon substrate.However, it is also possible to apply the method to the case where apoly crystal layer is formed on a silicon substrate surface. The reasonis that, the silicon layer which is alternately stacked with the nickellayer has an amorphous state, and nickel atoms easily diffuse into theamorphous rather than the crystal. Therefore, according to the presentinvention, it is possible to form a nickel monosilicide film having asufficient thickness even if the substrate surface is made of a polysilicon or a poly silicon-germanium with a small consumption of siliconor silicon-germanium of the substrate.

In addition, in the second embodiment of the present invention, thesubstrate may be not only a usual silicon substrate but also a siliconon insulator (SOI) substrate or a silicon-germanium on insulator (SGOI)substrate. In this case, it is possible to prevent from degrading a MOStransistor performance which is caused by reaching of nickel silicidecontaining nickel monosilicide as a main composition to the buried oxidelayer when the MOS transistor is fabricated on a thin SOI or SGOI layer.

Also, as explained in the first embodiment, instead of forming a nickellayer and a silicon layer, a co-deposition layer of nickel and siliconmay be used for forming a nickel silicide film through a silicidereaction after the deposition.

Furthermore, as explained in the first embodiment, it may be possible toimplement a preliminary thermal treatment of which temperature is lowerthan the second substrate temperature before implementing the secondthermal treatment.

Third Embodiment

Next, a third embodiment of the present invention will be explained.FIG. 5A to FIG. 5E are, in the third embodiment of the presentinvention, partial traverse cross sectional views showing each processrelating to a nickel silicide film formation method when a nickelsilicide film is applied to a contact of a source/drain and a gateelectrode. FIG. 5A is a partial traverse cross sectional view of a MOStransistor before forming the contact of nickel silicide. Deviceisolation region 42, gate insulator film 43, source/drain region 44,gate electrode 45, and gate sidewall 46 are formed on silicon substrate41.

As shown in FIG. 5B, exposure and etching are conducted using masksafter coating a resist on a whole surface, and resist 47 is left only onthe device isolation region and the gate sidewall. Next, as shown inFIG. 5C, as with the first and second embodiments, nickel layer 48 andsilicon layer 49 are alternately deposited. In this process, a stackedlayer structure of nickel and silicon is formed on the whole substrateusing, for example, a usual sputtering method or a molecular beamepitaxy method.

Next, by implementing a thermal treatment similar to the first andsecond embodiments, as shown in FIG. 5D, nickel silicide film 410 isformed. After that, using an etchant which has an etching selectivityagainst the resist, the nickel silicide film formed on the gate sidewalland the device isolation region is removed together with the resist forfabricating a MOS transistor which is formed nickel silicide contacts onthe source/drain region and the gate electrode as shown in FIG. 5E.

A MOS transistor fabricated through the above process is able to reducea contact resistance because it has a contact of nickel silicide filmhaving a sufficient thickness, thereby resulting in increase intransistor performance. In addition, since the silicide film is formedwithout consuming substantial silicon at the source/drain region, adistance between the p-n junction at the source/drain region and thesilicide film is large enough. Then, a degradation due to junctionleakage is few.

(A Fabrication Method of a Semiconductor Device)

Next, a fabrication method of a semiconductor device will be explained.

The fabrication method of a semiconductor device according to thepresent invention, which uses a nickel silicide film formation methoddescribed in the above, comprises a stacked film formation process foralternately stacking at least one nickel layer and at least one siliconlayer on a substrate having a semiconductor region and an insulator filmregion on a surface of the substrate at a first substrate temperaturewhich does not cause a silicide reaction, a silicide reaction processfor conducting a thermal treatment of the stacked layer film at a secondsubstrate temperature which causes a formation of nickel monosilicide,and an etching process for removing a film formed on the insulator filmby etching, wherein, in the stacked film formation process, a ratio(N_(Ni)N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) in the whole stacked layer filmis equal to or more than 1.

In the present invention, the each process may be one of a continuousprocess in some case, and may be an independent process to each other inother case.

In the fabrication method of the present invention, a fundamentalfeature of the nickel silicide film formed through the stacked filmformation process and the silicide reaction process is the same withwhat is described in the explanation of the nickel silicide formationmethod. However, the features of the present invention are toalternately deposit a nickel layer and a silicon layer on thesemiconductor region and the insulator region on the substrate so thatthe ratio (N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni))to the number of total silicon atoms (N_(si)) in the whole stacked layerfilm is equal to or more than 1, and to have a different composition ofthe nickel silicide film on the semiconductor region and the insulatorregion after the silicide reaction. A nickel silicide film formed on theinsulator region is easily etched due to rich of nickel, as a result, anickel rich region of the nickel silicide film on the insulator regioncan be selectively etched with ease.

That is, although silicide is formed though the reaction of nickel andsilicon deposited on a substrate where the insulator is exposed, thenickel can not diffuse into the insulator, thereby does not react withatoms composing the insulator. Therefore, on the insulator, nickelsilicide having a composition ratio of nickel and silicon correspondingto a ratio of the number of the deposited nickel atoms and silicon atomsis formed. In the present invention, since the deposition is conductedso that the number of nickel atoms is larger than that of silicon atoms,nickel-rich nickel silicide is formed on the insulator region. On theother hand, on the semiconductor region of silicon region, since a partof the deposited nickel atoms diffuse into the substrate and react withsilicon atoms in the substrate, the formed nickel silicide film iscrystallized by succeeding a crystallity of single crystal silicon orpoly crystal silicon of the substrate, and has a grain size with acertain level having a specific orientation. On the other hand, on theinsulator region, since the insulator is an amorphous state, the nickelsilicide film has a small grain size and no specific crystalorientation, thereby resulting in bad crystallity.

A nickel silicide film having excess nickel atoms and bad crystallitycan easily be removed with, for example, an etchant which is prepared bymixing hydrocloric acid, hydrogen peroxide, and water at some ratio. Inthis case, since the nickel silicide film on silicon has nickelmonosilicide (NiSi) as a main composition and a good crystallity, thefilm is etched little.

Therefore, according to the present invention, it is possible to form anickel silicide film having a sufficient thickness and low resistivity,as well as suppressing consumption of silicon atoms in the siliconsubstrate as much as possible. In addition, it is also possible to forma nickel silicide film only on single crystal or poly crystal silicon byremoving the nickel silicide film formed on the insulator region by wetetching. If the method of the present invention is applied to afabrication process of a MOS transistor, a salicide process, which formsnickel silicide only on single crystal silicon of a source/drain regionand poly crystal silicon of a gate electrode, can be employed byremoving nickel silicide on a silicon oxide film or a silicon nitridefilm of the device isolation region and the gate sidewall by wetetching.

Regarding the nickel silicide film to be etched, it is favorable thatthe ratio (N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni))to the number of total silicon atoms (N_(si)) in the whole region isequal to or more than 1.11 (Ni:Si=1:less than 0.9), 1.25 (Ni:Si=1:lessthan 0.8) is more favorable, and 1.43 (Ni:Si=1:less than 0.70) isfurther favorable. Nickel silicide films having the above compositionsare easily etched by the etchant. This is quite different from the factthat, for example, a nickel silicide film having a ratio (N_(Ni)/N_(si))of 1.00 (Ni:Si=1:1) is not etched.

The above-described composition may be a composition of entire nickelsilicide film, or may be a composition at an interface adjacent to theinsulator region. That is, at least the composition at the interfaceadjacent to the insulator region must be within the range, and thenickel silicide film is etched at least at the interface by erosion ofthe etchant. Nickel and silicon compositions in the above are results ofanalysis, for example, with X-ray Photoelectron Spectroscopy (XPS)

The silicide film is etched most favorably when the X-ray diffractionpattern has a diffraction peak of Ni2Si.

FIG. 6 is a figure showing a X-ray diffraction pattern of a nickelsilicide film which is formed on Si composing a semiconductor region andon SiO2 composing an insulator region with a condition that the ratio(N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) in the whole stacked layer filmis 2 (Ni:Si=1:0.5), and implemented the silicide reaction after thatwith annealing at 400° C.

A diffraction peak of nickel monosilicide (NiSi) can be seen on the Si.On the other hand, a diffraction peak of NiSi2 is seen on the SiO2.Inventors of the present invention have confirmed that when a silicidefilm having the above diffraction pattern was etched, a silicide on SiO2having a diffraction peak of Ni2Si had been selectively etched. TEMphotographs before and after the etching are shown in FIG. 7 and FIG. 8.That is, FIG. 7 is a cross sectional. TEM photograph of Ni2Si formed onSiO2 before the etching. FIG. 8 is a cross sectional TEM photograph ofNi2Si formed on SiO2 after the etching. From FIG. 8, it has beenconfirmed that the Ni2Si formed on SiO2 had disappeared by the etching.

In addition, as explained in the first embodiment, a nickel silicidefilm may be formed by causing the above-described silicide reactionafter co-deposition of nickel and silicon. In this case, a compositionalratio (N_(Ni)/N_(si)) of nickel and silicon at the deposition is equalto or more than 1 as with the above. A film formed through the aboveco-deposition is caused the silicide reaction by implementing a thermaltreatment at the second substrate temperature described in the above. Itwas found that the film after the silicide reaction becomes as follows.(i) A nickel silicide film on Si composing a semiconductor region hasbecome a nickel monosilicide film, which is unable to be etched, sincethe excess nickel atoms are consumed by diffusing into silicon. (ii) Anickel silicide film on SiO2 composing an insulator region has become aNi2Si film, which is easily etched, since the excess nickel atoms cannot diffuse into SiO2. As a result, as described before, a nickelsilicide film only on SiO2 of insulator film can be selectively etched.Regarding a method for co-deposition of nickel and silicon, variousdeposition methods, for example, a reactive spattering method or a CVDmethod may be adopted.

Further, as explained in the first embodiment, a preliminary thermaltreatment at a low temperature may be implemented before the thermaltreatment at the second substrate temperature. It is favorable that atemperature of the preliminary thermal treatment is lower than that of arange of the second substrate temperature. If a high temperature thermaltreatment is suddenly implemented at the beginning, there is apossibility to cause variations of, for example, composition andthickness of the nickel silicide film due to locally abnormaltemperature rise. However, by implementing the preliminary thermaltreatment at a low temperature, a change of crystallity of the nickeland silicon layers composing the stacked layer film is caused withoutcausing complete silicide reaction. That is, the nickel layer and thesilicon layer are changed from the amorphous state to a highercrystalline state. Also, when silicon and nickel are co-deposited toform a co-deposited film containing silicon and nickel, the co-depositedfilm is also changed from the amorphous state to a higher crystallinestate.

In the present embodiment, the stacked layer film or the co-depositedfilm is formed on a surface of the semiconductor region and theinsulator region. The semiconductor region has a higher crystallity thanthe insulator region in general. Typically, the insulator region is anamorphous state, on the other hand, the semiconductor region is acrystalline state. The stacked layer film or the co-deposited film is anamorphous state. By implementing the preliminary thermal treatment, thestacked layer film or the co-deposited film is changed from theamorphous state to a higher crystalline state. The change on thesemiconductor region is more remarkable than that on the insulatorregion. That is, since a crystallity of the semiconductor region ishigher than that of the insulator region, a difference of thecrystallity between these two regions which compose the base of the filmeffects to the change from the amorphous state to the higher crystallinestate of the stacked layer film or the co-deposited film. That is, astacked layer film or a co-deposited film located on a semiconductorregion which has a higher crystallity becomes a high crystalline stateby receiving effect of the base having a high crystallity. On the otherhand, a part of stacked layer film or a co-deposited film located on aninsulator region having a low crystallity becomes a low crystallinestate by receiving the effect of the base having a low crystallity. Forexample, a region of a stacked layer film or a co-deposited film locatedon a semiconductor region of a single crystal state becomes a singlecrystal state or a state close to a single crystal state by conducting apreliminary thermal treatment at a lower temperature than the range ofthe second substrate temperature. On the other hand, a region of astacked layer film or a co-deposited film located on an insulator regionof an amorphous state does not change from the amorphous state, orchanges little from the amorphous state. Therefore, the stacked layerfilm or the co-deposited film conducted the preliminary thermaltreatment has a high crystallity on the semiconductor region and a lowcrystallity on the insulator region.

Then, as already explained in the present embodiment, by implementingthe thermal treatment at the second substrate temperature, the silicidereaction is caused to form a nickel silicide film. After that, asexplained in the above, by removing a nickel rich region on theinsulator region through selective etching, a nickel silicide filmcomposed of only nickel monosilicide area on the semiconductor regioncan be formed with a self-aligning manner.

A nickel silicide film can be formed with a self-aligning manner even ifthe etching process is implemented before the silicide reaction process.As described before, a stacked layer film or a co-deposited filmimplemented the preliminary thermal treatment has a higher crystallityon the semiconductor region and a lower crystallity on the insulatorregion. The difference of the crystallity has an effect on etching rate.That is, a higher crstallity region has a lower etching rate than alower crystallity region. Using this fact, by dipping the entire stackedlayer film or the co-deposited film in the etchant, only the lowercrystallity region located on the insulator region is selectivelyetched, while leaving the higher crstallity region on the semiconductorregion. As a result, the etching can be achieved with a self-aligningmanner. After that, by implementing a thermal treatment at the secondsubstrate temperature, thereby causing the silicide reaction of thestacked layer film or the co-deposited film remained on thesemiconductor region, the nickel silicide film can be formed with aself-aligning manner only on the semiconductor region.

As described before, an additional advantage of implementing thepreliminary thermal treatment at a low temperature is to slow down thetemperature rise. As a result, a nickel silicide film can stably beformed without causing variations of, such as, composition and thicknessof the film.

Fourth Embodiment

Next, a semiconductor device fabrication method of a fourth embodimentof the present invention will be explained. FIG. 9A to FIG. 9D arepartial traverse cross sectional views showing each process according toone example of method of the fourth embodiment of the present inventionfor forming a nickel silicide film containing nickel monosilicide as amain composition on a source/drain region and on a gate electrode of aMOS transistor on a silicon substrate with a self-aligning manner. FIG.10 is a partial enlarged traverse cross sectional view of a MOStransistor shown in FIG. 9B. In this embodiment, as with the aboveembodiments, a nickel monosilicide film means a nickel silicide filmcontaining nickel monosilicide as a main composition.

First, as shown in FIG. 9A, device isolation region 72, gate insulatorfilm 73, gate electrode 74, gate sidewall 75, and source/drain region 76are formed on silicon substrate 71 with a usual fabrication process of aMOS transistor. In the figure, device isolation region 72 and gatesidewall 75 are formed with an insulator film such as a silicon oxidefilm and a silicon nitride film, and poly crystal silicon is used forgate electrode 74. Further, source/drain region 76 is formed by ionimplantation of dopant impurity such as boron or arsenic into substratesilicon 7, followed by an activation anneal.

Next, as shown in FIG. 9B and FIG. 10, stacked layer film 77 alternatelystacking nickel layer 78 and silicon layer 79 on the entire substrate isformed. FIG. 10 is an enlarged figure of stacked layer film 77. Nickellayer 78 is formed first on the substrate and silicon layer 79 is formednext. Three sets of nickel layer 78 and silicon layer 79 are stacked onthe substrate. Nickel layer 78 and silicon layer 79 can be formed bydepositing nickel atoms and silicon atoms using optionally, for example,a spattering method or a molecular beam epitaxy method. However, asubstrate temperature during the deposition must be maintained at lessthan 200 C so that silicon layer 79 becomes amorphous silicon, and alsonickel and silicon do not react during the deposition.

Regarding the thicknesses of nickel layer 78 and silicon layer 79, theymust be controlled so that a ratio (N_(Ni)/N_(si)) of the number oftotal nickel atoms (N_(Ni)) to the number of total silicon atoms(N_(si)) in the whole stacked layer film 77 is equal to or more than 1.In other words, N_(Ni):N_(si) must be 1:less than 1. Deposition forms ofthe nickel layer and the silicon layer are similar to those of describedin explanation of the nickel silicide film formation method. When aratio of a total silicon layer thickness to a total nickel layerthickness is 1.79, the ratio (N_(Ni)/N_(si)) of the number of totalnickel atoms (N_(Ni)) to the number of total silicon atoms (N_(si)) inthe whole stacked layer film 77 is equal to 1. Then, if the number ofnickel atoms larger than that of silicon atoms is required, it can beachieved by making the ratio of the total silicon layer thickness to thetotal nickel layer thickness is less than 1.79.

Regarding the order of stacking of a nickel layer and a silicon layer,the silicon layer may be deposited at the nearest layer to the substrateby reversing the order of the stacking. If the silicon layer isdeposited at the upper most layer, it is possible to prevent fromoxidizing the deposited nickel layer during a time between taking outthe substrate out of the apparatus after deposition and implementing thethermal treatment.

Next, as shown in FIG. 9C, nickel monosilicide film 710 is formed on asource/drain region and on a gate electrode, both of where silicon isexposed, by implementing a thermal treatment at a second temperaturewhich is higher than that of a substrate temperature when nickel andsilicon are deposited. The thermal treatment method, the temperature andthe atmosphere of the thermal treatment are similar to those of themethod of the above-described nickel silicide film formation method,then, the explanations are omitted.

In the present embodiment, a nickel monosilicide film is formed throughthe reaction of the deposited nickel atoms and silicon atoms. In thiscase, in the source/drain region and the gate electrode where silicon isexposed, since the number of nickel atoms is larger than that of siliconatoms, thereby existing sufficient excess nickel atoms more thannecessary for forming nickel monosilicide, nickel monosilicide is formedby causing the silicide reaction through diffusion of a part of theexcess nickel atoms into the exposed silicon. On the other hand, if thenumber of deposited silicon atoms is larger than that of nickel atoms,for example, the excess silicon atoms are left without reaction in somecase, or nickel disilicide is formed in other case. Then, the obtainednickel silicide film becomes non-uniform, and has a poor crystallity anda high resistivity. Therefore, in the present invention, the nickellayer and the silicon layer are deposited so that a ratio(N_(Ni)/N_(Si)) of the number of total nickel atoms (N_(Ni)) to thenumber of total silicon atoms (N_(si)) existing in the whole stackedlayer film becomes equal to or more than 1, in other words,N_(Ni):N_(si) becomes 1:less than 1. Accordingly, the excess nickelatoms diffuse into the substrate silicon and react with it to form anickel silicide film containing uniform and higher crystalline nickelmonosilicide as a main composition. In this case, nickel atoms whichreact with the substrate silicon are ones left without reaction with thedeposited silicon atoms.

On the other hand, as shown in FIG. 9C, nickel and silicon deposited ona device isolation region and a gate sidewall where an insulator film isexposed also react to form nickel silicide film 711. However, since thenickel does not react with atoms composing the insulator film, nickelsilicide having a composition corresponding to the ratio of the numberof deposited nickel atoms and that of silicon atoms is formed on theinsulator film. In the present invention, as described in the above, thedeposition is implemented so that the number of nickel atoms are largerthan that of silicon atoms, then, nickel-rich nickel silicide is formedon the insulator film. In addition, on the silicon region, since a partof the deposited nickel atoms react with silicon atoms in the substrate,the formed nickel silicide film is crystallized by succeeding acrystallity of single crystal silicon or poly crystal silicon of thesubstrate, and has a grain size with a certain level having a specificorientation. On the other hand, on the insulator region, since theinsulator is an amorphous state, the nickel silicide film has a smallgrain size and no specific crystal orientation, thereby resulting in apoor crystallity. Such a nickel silicide film which is nickel-rich andhas a poor crystallity is easily removed by an appropriate etchant. Inthis case, a nickel silicide film on silicon has nickel monosilicide asa main composition and a good crystallity. Then, the film is etchedlittle.

Therefore, by dipping the whole substrate after the thermal treatment inan appropriate etchant, for example, a mixture of hydrochloricacid:hydrogen peroxide solution:water 1:1:6, as shown in FIG. 9D, astructure having nickel silicide, only on the source drain region andthe gate electrode part can be formed by removing the film formed on theinsulator film. Regarding the etchant, any solution which etches nickelmonosilicide little and, on the other hand, easily etches nickel-richnickel silicide is usable. Such solutions other than the above are, forexample, a mixture of sulfuric acid, hydrogen peroxide, and water, and amixture of ammonia water, hydrogen peroxide, and water. In addition, forpromoting the etching reaction and for entirely removing the nickelsilicide on the insulator film, for example, methods for changing themixing ratio of the chemicals, heating the solution, and combiningseveral solutions may be used.

In the fourth embodiment, substrates of a silicon on insulator (SOI) anda silicon-germanium on insulator (SGOI) may be used as well as a usualsilicon substrate 81.

In addition, as explained in the third embodiment, a nickel silicidefilm may be formed by causing the above-described silicide reactionafter co-depositing nickel and silicon instead of forming a stackedlayer film of a nickel layer and a silicon layer.

Furthermore, as explained in the first embodiment, a preliminary thermaltreatment at a low temperature may be conducted before implementing athermal treatment at the second substrate temperature. In addition, asexplained in the fourth embodiment, after conducting etching withself-aligning manner by making use of difference of the film crystallitybetween the semiconductor region and insulator region after thepreliminary thermal treatment at a low temperature, a silicide reactionmay be caused by conducting a thermal treatment at the second substratetemperature.

Fifth Embodiment

Next, a semiconductor device fabrication method of a fifth embodiment ofthe present invention will be explained. The fifth embodiment of thepresent invention is different from the above fourth embodimentregarding a source/drain region and a gate electrode. That is, in thefifth embodiment, the source/drain region and the gate electrode arecomposed of silicon-germanium mixed crystal and silicon-germanium polycrystal, respectively. FIG. 11A to FIG. 11B are partial traverse crosssectional views showing each process according to one example of methodof the fifth embodiment of the present invention for forming a nickelsilicide film containing nickel monosilicide as a main composition onthe source/drain region and the gate electrode of a MOS transistor on asilicon substrate with a self-aligning manner. Recently, for increasinga performance of a MOS transistor, a use of silicon-germanium mixedcrystal for the source/drain region End a use of silicon-germanium polycrystal for the gate electrode have been proposed. The fifth embodimentmay also be applicable to these.

In the fifth embodiment, as shown in FIG. 11A, gate electrode 84 is madeof silicon-germanium poly crystal and source/drain region 86 is made ofsilicon-germanium mixed crystal. This is realized through the followingprocesses. For example, in the usual MOS transistor fabrication process,silicon-germanium poly crystal is grown instead of growing poly crystalsilicon at the gate electrode formation process, and silicon-germaniummixed crystal is grown through selective epitaxial growth with, forexample, CVD after removing a silicon layer once by etching on thesource/drain region after the gate electrode formation. Otherwise, itmay be possible to deposit silicon-germanium mixed crystal withselective epitaxial growth without etching the source/drain region. InFIG. 11A, symbol 81 is a silicon substrate, symbol 82 is a deviceisolation region, symbol 83 is a gate insulator film, and symbol 85 is agate sidewall.

For a structure shown in FIG. 11A, as with the method similar to thefourth embodiment, first, a nickel layer and a silicon layer arealternately deposited at a first substrate temperature. In theabove-described fourth embodiment, a deposition temperature was set atless than 200° C., so as to make the silicon layer an amorphous state,and not to react nickel and, silicon and silicon-germanium mixed crystalto each other during the deposition. In this case, as with the fourthembodiment, thicknesses of the nickel layer and the silicon layer arealso configured so that a ratio (N_(Ni)/N_(si)) of the number of totalnickel atoms (N_(Ni)) to the number of total silicon atoms (N_(si))existing in the whole stacked layer film becomes equal to or morethan 1. However, the thicknesses and the number of layers of the nickellayer and the silicon layer can be varied according to a requiredthickness of a nickel monosilicide film.

Next, a thermal treatment at the second temperature which is higher thanthe first temperature is conducted, followed by removing nickel silicideon an insulator film using an etchant similar to the fourth embodiment,then, as shown in FIG. 11B, a structure which is formed nickelmonosilicide film 810 on source/drain region 86 and gate electrode 84 isobtained. In this case, since a part of nickel atoms diffuse intosilicon-germanium mixed crystal and react with it at gate electrode 84and source/drain region 86, a nickel germanosilicide (NiSi_(1-x)Ge_(x))layer 812 is formed on gate electrode 84 composed of nickel monosilicidefilm 810 and the silicon-germanium mixed crystal layer, and source/drainregion 86. In the fifth embodiment, it is favorable that the secondtemperature for the thermal treatment is also less than 750° C. so thatnickel monosilicide is well formed and not to cause a disilicidereaction.

According to a conventional method in which only nickel is deposited andthermally treated, the formed film entirely becomes nickelgermanosilicide. Also, it is likely to form defects at the interfacebetween the nickel germanosilicide layer and the silicon-germanium mixedcrystal layer by germanium precipitation. However, in the presentembodiment, through reaction of substantial nickel atoms with thedeposited silicon layer, it is possible to make the formed nickelgermanosilicide layer 812 extremely thin. A resistivity of nickelgermanosilicide increases according to increase in concentration ofgermanium. A nickel germanosilicide film according to the presentembodiment has a lower resistivity than that of the conventional methodin which the film is prepared by deposition of only nickel and thermaltreatment. In addition, during the thermal treatment, a diffusion ofgermanium atoms in nickel germanosilicide film takes place, therebydecreasing concentration of germanium atoms in the nickelgermanosilicide film, resulting in further lowering of the resistivity.

In the present invention, it is also possible to deposit a silicon layerat the nearest layer to the substrate by reversing the order ofdeposition of the nickel layer and the silicon layer. This is the samewith the fourth embodiment.

As described before, according to the semiconductor device fabricationmethod of the present invention, it is possible to form a nickelmonosilicide film 810 with sufficient thickness, while suppressingsilicon-germanium consumption of the substrate even if source drainregion 86 and gate electrode 84 are silicon-germanium mixed crystal andpoly silicon-germanium, respectively. In addition, in the fifthembodiment, the substrate may be a silicon on insulator (SOI) substrate,or a silicon-germanium on insulator (SGOI) substrate, as well as usualsilicon substrate 81.

Further, as explained in the third embodiment, a nickel silicide filmmay be formed through the silicide reaction after co-depositing nickeland silicon instead of forming a nickel layer and a silicon layer.

Furthermore, as explained in the first embodiment, a preliminary thermaltreatment at a low temperature may be implemented before the secondsubstrate temperature. In addition, as explained in the above fourthembodiment, it is possible to cause the silicide reaction byimplementing a thermal treatment at the second substrate temperatureafter etching the substrate with a self-aligning manner using thedifference of crystallity on the semiconductor region and the insulatorregion due to the preliminary thermal treatment at a low temperature.

Sixth Embodiment

Next, a semiconductor device fabrication method in the sixth embodimentof the present invention will be explained. As an example of the sixthembodiment, the example applying the present invention to a MOStransistor on SOI substrate will be described. FIG. 12 is a partialtraverse cross sectional view showing a MOS transistor on a SOIsubstrate which is formed a nickel silicide film using the sixthembodiment of the present invention with a method similar to the fourthand fifth embodiments. In FIG. 12, the MOS transistor includes siliconsubstrate 91, device isolation region 92, gate insulator film 93, gateelectrode 94 composed of poly crystal silicon, and gate sidewall 95.

In the sixth embodiment, source/drain region 96 is formed in a SOI layeron buried oxide layer 913. In a thin SOI, a thickness of the SOI layermay be about 10 nm. If the present invention is applied, a thick nickelmonosilicide film 910 can be formed by suppressing silicon consumptionof the SOI layer. For example, if nickel monosilicide film 910 of 20 nmin thickness is formed with a condition that a ratio (N_(Ni)/N_(si)) ofthe number of total nickel atoms (N_(Ni)) to the number of total siliconatoms (N_(si)) existing in the whole stacked layer film is equal to 1.5(N_(Ni):N_(si)=1:0.66), a thickness of the consumed silicon of the SOIlayer will be 5 nm, thereby leaving a sufficient distance between thenickel monosilicide film 910 and buried oxide layer 913. In theconventional method in which only nickel is deposited and annealed, ifthe consumed silicon thickness of the SOI layer is 5 nm, a thickness ofthe nickel monosilicide film will be about 6 nm. Therefore, a sheetresistance of the conventional film will be more than three times ofthat of nickel monosilicide film 910 of 20 nm in thickness according tothe present invention. Accordingly, in a MOS transistor on the SOIsubstrate, it is possible to increase performance of the MOS transistorcompared with the conventional one, as well as preventing from degradingthe MOS transistor performance due to reaching of nickel monosilicidefilm 910 to the buried oxide layer 913.

In addition, as explained in the third embodiment, a nickel silicidefilm may be formed through a silicide reaction after co-depositingnickel and silicon instead of forming a stacked layer film of a nickellayer and a silicon layer.

Furthermore, as explained in the first embodiment, a preliminary thermaltreatment at a low temperature may be conducted before implementing athermal treatment at the second substrate temperature. In addition, asexplained in the fourth embodiment, after etching the substrate with aself-aligning manner using difference of crystallity of the film betweenthe semiconductor region and the insulator region after the preliminarythermal treatment at a low temperature, the silicide reaction may becaused by conducting a thermal treatment at the second substratetemperature.

Seventh Embodiment

Next, a semiconductor device fabrication method according to a seventhembodiment of the present invention will be explained. The presentinvention may be applicable to a MOS transistor which uses distortedsilicon or distorted silicon-germanium mixed crystal. FIG. 13 is apartial traverse cross sectional view showing a MOS transistor formed ona distorted silicon layer using the seventh embodiment of the presentinvention with a method similar to that of the above-described fourth tosixth embodiments.

In FIG. 13, silicon-germanium layer 115 is formed on silicon substrate101, and distorted silicon channel layer 114 and source/drain region 106are formed on a silicon layer which is formed on silicon-germanium layer115.

In this structure, a distortion of silicon-germanium insilicon-germanium layer 115 is being relaxed, and the silicon layerwhich is formed on this layer and containing distorted silicon channellayer 114 and source/drain region 106 is distorted because it isepitaxially grown on silicon-germanium layer 115, of which distortion isrelaxed. In a MOS transistor having a distorted silicon channel, thedistorted silicon channel 114 must be extremely thin for applyingdistortion to the silicon layer. A thickness of the silicon layercontaining the distorted silicon channel 114 and source/drain region 106is about 10 nm. Then, if the present invention is applied, as with shownin the sixth embodiment, since it is possible to prevent from reachingof nickel monosilicide film 110 to silicon-germanium layer 115, as wellas small silicon consumption of the distorted silicon layer, it becomespossible to prevent from relaxing the distortion of source/drain region106 and distorted silicon channel region 114 during silicidation of thefilm.

If nickel monosilicide film 110 reaches to silicon-germanium layer 115,a current leaks through silicon-germanium layer 115. In addition, if thedistorted channel region is relaxed, the increase of the MOS transistorperformance due to the distorted channel can not be achieved. Then, byapplying the present invention to the distorted channel MOS transistor,it becomes possible to prevent from degrading the transistor performanceand to sufficiently extract performance of the distorted channel MOStransistor. In FIG. 13, symbol 102 is a device isolation region, symbol103 is a gate insulator film, symbol 104 is a gate electrode composed ofpoly crystal silicon, and symbol 105 is a gate sidewall.

In addition, as explained in the third embodiment, a nickel silicidefilm may be formed through a silicide reaction after co-depositingnickel and silicon instead of forming a stacked layer film of a nickellayer and a silicon layer.

Furthermore, as explained in the first embodiment, a preliminary thermaltreatment at a low temperature may be conducted before implementing athermal treatment at the second substrate temperature. In addition, asexplained in the fourth embodiment, after etching the substrate with aself-aligning manner using a difference of crystallity of the filmbetween the semiconductor region and insulator region after thepreliminary thermal treatment at a low temperature, the silicidereaction may be caused by conducting a thermal treatment at the secondsubstrate temperature.

Eighth Embodiment

Next, a semiconductor device fabrication method according to the eighthembodiment of the present invention will be explained. It is possible toapply the present invention to a metal gate MOSFET. FIG. 14A to FIG. 14Dare partial traverse cross sectional views showing each processaccording to one example of method of the eighth embodiment of thepresent invention for forming a nickel silicide film containing nickelmonosilicide as a main composition on a source/drain region and a gateelectrode of a MOS transistor on a silicon substrate with aself-aligning manner.

First, as shown in FIG. 14A, after depositing gate insulator film 203and gate electrode (metal) 204 on silicon substrate 201 which is formeddevice isolation region 202, cap layer 205 composed of a silicon oxidefilm or a silicon nitride film is formed. After that, a gate structureis fabricated with lithography and dry etching. Regarding cap layer 205,such a film as a silicon oxide film or a silicon nitride film, whichdoes not react with nickel and silicon deposited at later process and isstable against tie etchant during the etching of nickel monosilicide,may be applicable to the film.

Next, after forming a silicon oxide film on the entire substrate, gatesidewall 206 as shown in FIG. 14B is fabricated with dry etching. Caplayer 205 formed in the process shown in FIG. 14A is left on gateelectrode 204.

Next, stacked layer film 208 of nickel and silicon shown in FIG. 14C isformed with a method similar to that of the above-described embodiments.After that, as shown in FIG. 14D, nickel monosilicide (NiSi) layer 209is formed only on source/drain region 207 with etching after annealing.Cap layer 205 on gate electrode 207 is removed by etching when a contactis formed on gate electrode 204.

In addition, as explained in the third embodiment, a nickel silicidefilm may be formed through a silicide reaction after co-depositingnickel and silicon instead of forming a stacked layer film of a nickellayer and a silicon layer.

Furthermore, as explained in the first embodiment, a preliminary thermaltreatment at a low temperature may be conducted before implementing athermal treatment at the second substrate temperature. In addition, asexplained in the fourth embodiment, after etching the substrate with aself-aligning manner using a difference of crystallity of the filmbetween the semiconductor region and insulator region after thepreliminary thermal treatment at a low temperature, the silicidereaction may be caused by conducting a thermal treatment at the secondsubstrate temperature.

Example of Embodiment

The present invention will be further explained specifically below,

An apparatus for molecular beam epitaxy (MBE) was emplyed as a filmformation apparatus. After forming a nickel layer first on a siliconsingle crystal substrate with (100) orientation at a first substratetemperature of 50° C., a silicon layer and a nickel layer werealternately deposited on it, five layers for each in total. After that,in a vacuum atmosphere of the MBE apparatus, a thermal treatment wasimplemented 30 minutes at the second substrate temperature of 400° C. InTable 1 below, film thicknesses of each nickel layer and silicon layerwhen they were varied, and sheet resistances of the nickel silicide filmobtained after the thermal treatment are shown. TABLE 1 thickness ofthickness of number of thermal treatment Ni layer Si layer stacked layertemperature sheet resistance sample (nm) (nm) (frequency) (°C./Centigrade) (Ω/sq.) A 2 5 5 400 38 B 2 2.5 5 400 9.7 C 2 2 5 400 9.5*) Ω/sq. = Ω/cm²

As described before, when total Si thickness/total Ni thickness is equalto 1.79, a ratio of the number of Ni atoms:the number of Si atomsbecomes 1:1 from a calculation using atomic mass and specific gravity ofNi and Si.

As shown in Table 1, in sample A, since thicknesses of the Ni layer andthe Si layer are 2 nm and 5 nm, respectively, then, Si thickness/Nithickness=2.5. Therefore, Si atoms are more than Ni atoms in sample A.In this case, a nickel silicide having favorable nickel monosilicide wasnot formed, but nickel disilicide having a high sheet resistance wasformed.

On the other hand, in sample B, since thicknesses of the Ni layer andthe Si layer are 2 nm and 2.5 nm, respectively, then, Si thickness/Nithickness=1.25. Therefore, Ni atoms are more than Si atoms in sample B.Also, in sample C, since thicknesses of the Ni layer and the Si layerare 2 nm and 2 nm, respectively, then, Si thickness/Ni thickness=1.Therefore, Ni atoms are also more than Si atoms in sample C. In thesecases, since nickel monosilicide having a favorable low resistivity hasbeen formed, a low sheet resistance was obtained. In addition,thicknesses of sample B and sample C were measured. Using thethicknesses and the sheet resistances in Table 1, the resistivity wascalculated. As a result, it has been found that the resistivity wasabout 14˜17 μΩcm. From the result of the resistivity data, it has beenconfirmed that a nickel silicide film composed of favorable nickelmonosilicide had been formed. In addition, from results of X-raydiffraction measurement and transmission electron spectroscopyobservation, it has been confirmed that favorable nickel monosilicidefilms were formed in sample B and sample C.

In the present example of the embodiment, for example in sample C, athickness of nickel silicide film composed of nickel monosilicide wasabout 18 nm from observation result of transmission electronspectroscopy. In this case, in sample C, silicon atoms corresponding toabout 15 nm in film thickness might have been consumed if it iscalculated using a consumption factor 0.82. In sample C, a thickness ofthe total deposited silicon layer was about 10 nm, then, it was supposedthat the all silicon atoms had reacted with nickel atoms to form nickelmonosilicide. Therefore, silicon atoms of the silicon substrate amongthe total silicon atoms consumed for the reaction with nickel atomscorrespond to 5 nm in thickness. Accordingly, in the present example ofthe embodiment, it has been confirmed that a nickel silicide film havinga sufficient thickness of nickel monosilicide can be formed, whilesuppressing silicon consumption compared with the conventional method.

These results enable further progress of thinning of the advanced CMOSdevices in future. That is, in the advanced CMOS devices, it has beenforecasted that a depth of source/drain at contact formation regionwould become about 20 nm. However, if a conventional method in whichnickel is reacted only with a silicon Substrate is used, a thickness ofthe consumed silicon substrate must be less than half of source/draindepth, that is, less than 10 nm, for not to degrading performance of thetransistor. As a result, a thickness of nickel monosilicide becomes lessthan 12 nm because a consumption factor of nickel monosilicide is 0.82.Therefore, it has been difficult to form a nickel silicide film composedof nickel monosilicide with sufficient thickness for not to degradingjunction characteristic and for lowing the resistivity. However, insample B and sample C of the present examples of the embodiment, asdescribed in the above, since the nickel silicide film composed ofnickel monosilicide with sufficient thickness can be formed, it ispossible to respond sufficiently to the advanced CMOS devices, and itseffect is expectable.

As explained, according to the nickel silicide film formation method andthe semiconductor device fabrication method of the present invention, itis possible to provide a method for forming a nickel silicide filmhaving a sufficient thickness and a low resistivity, as well as a lowsilicon atom consumption of the substrate, thereby possible to achievehigh performance of a MOS transistor. In addition, if the presentinvention is applied to the case in which the substrate surface is asilicon-germanium mixed crystal layer and a poly silicon-germaniumlayer, a low resistivity film compared with the conventional method, inwhich only nickel is deposited and reacted, can be obtained as well aslow consumptions of silicon atoms and germanium atoms of the substrate.Also, if the present invention is applied to a SOI substrate and a SGOIsubstrate, a degradation of a MOS transistor performance due to reachingof the nickel silicide film to the buried oxide layer can be prevented.

Further, if the present invention is applied to a distorted channel MOStransistor formed with a semiconductor layer of which surface is formedwith a distorted silicon or distorted silicon-germanium layer, arelaxation of the distortion at the channel region during nickelmonosilicide formation can be suppressed as well as preventing fromreaching of the nickel monosilicide film to the silicon-germanium layer.With the above, a performance degradation of the distorted channel MOStransistor can be prevented and an original performance of the distortedchannel MOS transistor can be extracted.

According to the semiconductor device fabrication method of the presentinvention, since only a nickel silicide film on the insulator film canselectively be etched after causing the silicide reaction of the stackedlayer film, a fabrication efficiency of the semiconductor device havinga nickel monosilicide film can be increased.

According to the nickel silicide etching method of the presentinvention, since a nickel-rich nickel silicide film can selectively beetched, an efficient etching process can be achieved.

POSSIBILITY FOR INDUSTRIAL APPLICATION

The present invention is applicable to any method if the method isrelated to a method for forming nickel monosilicide with a sufficientthickness and a low resistivity, to a semiconductor fabrication methodusing the same, and to a method for selectively etching a nickel-richsilicide film of a nickel silicide film, and it has no limitation in thepossibility of its application.

While the present invention has been described by associating with somepreferred embodiments and examples, it is to be understood that theseembodiments and examples are merely for illustrative of the invention byan example, and not restrictive. While it will be obvious to thoseskilled in the art that various changes and substitutions by equivalentcomponents and techniques are eased upon reading the specification, itis believed obvious that such changes and substitutions fit into thetrue scope and spirit

1. A nickel silicide film formation method, comprising steps of: a stepfor forming a layer structure containing silicon and nickel on asubstrate at a first substrate temperature which does not cause asilicide reaction; and a step of the silicide reaction for formingnickel monosilicide by implementing a thermal treatment of the layerstructure at a second substrate temperature which causes a nickelmonosilicide reaction, wherein, in the step for forming the layerstructure, a ratio (N_(Ni)/N_(si)) of a number of total nickel atoms(N_(Ni)) to a number of total silicon atoms (N_(si)) existing in a wholelayer structure is equal to or more than
 1. 2. A nickel silicide filmformation method according to claim 1, wherein the step for forming thelayer structure is consist of co-depositing step of nickel and silicon.3. A nickel silicide film formation method according to claim 1, whereinthe step for forming the layer structure is consist of a stepalternately forming at least one nickel layer and at least one siliconlayer.
 4. A nickel silicide film formation method according to claim 3,wherein the layer structure is formed such that a ratio of the number ofnickel atoms in each nickel layer contained in the layer structure tothe number of silicon atoms in each silicon layer contained in the layerstructure is equal to a ratio of the number of total nickel atoms to thenumber of total silicon atoms existing in a whole layer structure.
 5. Anickel silicide film formation method according to claim 1, wherein theratio (N_(Ni)/N_(si)) of the number of total nickel atoms (N_(Ni)) tothe number of total silicon atoms (N_(si)) existing in the whole layerstructure is equal to or more than 1, and equal to or less than
 4. 6. Anickel silicide film formation method according to claim 1, wherein thenickel silicide contains the nickel monosilicide equal to or more than50%.
 7. A nickel silicide film formation method according to claim 1,wherein a region of at least one semiconductor selected from a group ofsingle crystal silicon, poly crystal silicon, distorted silicon, singlecrystal silicon-germanium, poly crystal silicon-germanium, and distortedsilicon-germanium is included in an uppermost surface of the substrate8. A nickel silicide film formation method according to claim 1, whereinsubstrate is any one selected from a group of a silicon substrate, a SOIsubstrate, and a SGOI substrate.
 9. A nickel silicide film formationmethod according to claim 1, wherein the layer structure formed with thestep of forming the layer structure is an amorphous state.
 10. A nickelsilicide film formation method according to claim 3, wherein eachthickness of the silicon layer and the nickel layer formed with the stepof forming the layer structure is in a range of 2 nm-10 nm.
 11. A nickelsilicide film formation method according to claim 1, wherein a surfaceorientation of a principal surface of the substrate is other than (111)surface.
 12. A nickel silicide film formation method according to claim1, further comprising a step of: a step for implementing a preliminarythermal treatment at a low temperature lower than the second substratetemperature after the step of forming the layer structure and before thestep of the silicide reaction.
 13. An etching method for etching anickel-rich region located on an insulator region of a nickel silicidefilm which is formed on at least one semiconductor region and at leastone insulator region on a substrate and a composition of the nickelsilicide film is different between the semiconductor region and theinsulator region, wherein a ratio (N_(Ni)/N_(si)) of a number of nickelatoms (N_(Ni)) to a number of on atoms (N_(si)) in the nickel-richregion is equal to or more than 1.11.
 14. An etching method according toclaim 13, wherein a region of the nickel silicide film located on thesemiconductor region is composed of nickel monosilicide and a region ofthe nickel silicide film located on the insulator region is composed ofnickel-rich nickel silicide.
 15. An etching method according to claim13, wherein the semiconductor region comprises at least onesemiconductor selected from a group of single crystal silicon, polycrystal silicon, distorted silicon, single crystal silicon-germanium,poly crystal silicon-germanium, and distorted silicon-germanium.
 16. Anetching method according to claim 13, wherein the insulator regioncomprises at least one selected from silicon oxide and silicon nitride.17. An etching method according to claim 13, wherein the nickel silicidefilm is formed with a step for forming a stacked layer film byalternately forming at least one nickel layer and at least one siliconlayer at a first substrate temperature which does not cause a silicidereaction, and a step of the silicide reaction for implementing a thermaltreatment of the stacked layer film at a second substrate temperaturewhich causes a nickel monosilicide reaction.
 18. An etching methodaccording to claim 17, wherein the silicon layer formed with the stepfor forming the stacked layer film is an amorphous state.
 19. An etchingmethod according to claim 17, wherein each thickness of the siliconlayer and the nickel layer :Formed with the step for forming the stackedlayer film is in a range of 2 nm-10 nm.
 20. An etching method accordingto claim 13, wherein the nickel silicide film is formed with a step forco-depositing nickel and silicon, and a step of a silicide reaction forimplementing a thermal treatment at a second substrate temperature whichcauses a nickel monosilicide reaction.
 21. An etching method accordingto claim 13, wherein the substrate is any one selected from a group of asilicon substrate, a SOI substrate, and a SGOI substrate.
 22. An etchingmethod according to claim 13, wherein a surface orientation of aprincipal surface of the substrate is other than (111) surface.
 23. Anetching method for etching a nickel-rich region located on an insulatorregion of a nickel silicide film which is formed on at least onesemiconductor region and at least one insulator region on a substrateand a composition of the nickel silicide film is different between thesemiconductor region and the insulator region, wherein the nickel-richregion has a diffraction peak of Ni₂Si in X-ray diffraction pattern. 24.An etching method according to claim 23, wherein a region of the nickelsilicide film located on the semiconductor region is composed of nickelmonosilicide and a region of the nickel silicide film located on theinsulator region is composed of nickel-rich nickel silicide.
 25. Anetching method according to claim 23, wherein the semiconductor regioncomprises at least one semiconductor selected from a group of singlecrystal silicon, poly crystal silicon, distorted silicon, single crystalsilicon-germanium, poly crystal silicon-germanium, and distortedsilicon-germanium.
 26. An etching method according to claim 23, whereinthe insulator region comprises at least one selected from silicon oxideand silicon nitride.
 27. An etching method according to claim 23,wherein the nickel silicide film is formed with a step for forming astacked layer film by alternately forming at least one nickel layer andat least one silicon layer at a fist substrate temperature which doesnot cause a silicide reaction, and a step of the silicide reaction forimplementing a thermal treatment of the stacked layer film at a secondsubstrate temperature which causes a nickel monosilicide reaction. 28.An etching method according to claim 27, wherein the silicon layerformed with the step for forming the stacked layer film is an amorphousstate.
 29. An etching method according to claim 27, wherein eachthickness of the silicon layer and the nickel layer formed with the stepfor forming the stacked layer film is in a range of 2 nm-10 nm.
 30. Anetching method according to claim 23, wherein the nickel silicide filmis formed with a step for co-depositing nickel and silicon, and a stepof a silicide reaction for implementing a thermal treatment at a secondsubstrate temperature which causes a nickel monosilicide reaction. 31.An etching method according to claim 23, wherein the substrate is anyone selected from a group of a silicon substrate, a SOI substrate, and aSGOI substrate.
 32. An etching method according to claim 23, wherein asurface orientation of a principal surface of the substrate is otherthan (111) surface.
 33. A semiconductor device fabrication method,comprising steps of: a step for forming a layer structure containingsilicon and nickel on at least one semiconductor region and on at leastone insulator region on a substrate at a first substrate temperaturewhich does not cause a silicide reaction; and a step of the silicidereaction for forming a nickel silicide film containing nickelmonosilicide, of which composition is different on the semiconductorregion and on the insulator region, by implementing a thermal treatmentof the layer structure at a second substrate temperature which causes anickel monosilicide reaction, wherein, in the step for forming the layerstructure, a ratio (N_(Ni)N_(si)) of a number of total nickel atoms(N_(Ni)) to a number of total silicon atoms (N_(si)) existing in a wholelayer structure is equal to or more than
 1. 34. A semiconductor devicefabrication method according to claim 33, wherein nickel silicidelocated on the semiconductor region after the silicide reaction step iscomposed of nickel monosilicide and the nickel silicide located on theinsulator region after the silicide reaction step is composed ofnickel-rich nickel silicide.
 35. A semiconductor device fabricationmethod according to claim 33, further comprising a step of: an etchingstep for removing the nickel-rich nickel silicide located on theinsulator region of the nickel silicide film by etching, thereby formingthe nickel silicide film only on the semiconductor region with aself-aligning manner.
 36. A semiconductor device fabrication methodaccording to claim 33, wherein the step for forming the layer structureis consist of co-depositing step of nickel and silicon.
 37. Asemiconductor device fabrication method according to claim 33, whereinthe step for forming the layer structure is consist of alternatelyforming at least one nickel layer and at least one silicon layer.
 38. Asemiconductor device fabrication method according to claim 33, whereinthe semiconductor region comprises at least one semiconductor selectedfrom a group of single crystal silicon, poly crystal silicon, distortedsilicon, single crystal silicon-germanium, poly crystalsilicon-germanium, and distorted silicon-germanium.
 39. A semiconductordevice fabrication method according to claim 33, wherein the insulatorregion comprises at least one selected from silicon oxide and siliconnitride.
 40. A semiconductor device fabrication method according toclaim 33, wherein the substrate is any one selected from a group of asilicon substrate, a SOI substrate, and a SGOI substrate.
 41. Asemiconductor device fabrication method according to claim 33, whereinthe layer structure formed with the step for forming the layer structureis an amorphous state.
 42. A semiconductor device fabrication methodaccording to claim 37, wherein each thickness of the silicon layer andthe nickel layer formed with the step for forming the layer structure isin a range of 2 nm-10 nm.
 43. A semiconductor device fabrication methodaccording to claim 33, wherein a surface orientation of a principalsurface of the substrate is other than (111) surface.
 44. Asemiconductor device fabrication method according to claim 33, furthercomprising a step of: a step for implementing a preliminary thermaltreatment at a low temperature lower than the second substratetemperature after the step for forming the layer structure and beforethe step of the silicide reaction.
 45. A semiconductor devicefabrication method according to claim 44, further comprising a step of:an etching step for etching off only a region closer to an amorphousstate having a poor crystallity located on the insulator region of thelayer structure before the silicide reaction step and after thepreliminary thermal treatment, thereby forming the nickel silicide filmonly on the semiconductor region with a self-aligning manner byimplementing the silicide reaction only for a remained region on thesemiconductor region of the layer structure.
 46. A nickel silicideformation method, comprising steps of: a step for forming a layerstructure containing silicon and nickel on at least one semiconductorregion and at least one insulator region on a substrate; and a step of asilicide reaction for forming a nickel silicide film having a nickelmonosilicide composition on the semiconductor region as well as having anickel-rich composition on the insulator region by implementing athermal treatment of the layer structure at a second substratetemperature which causes a nickel monosilicide reaction, wherein, in anickel-rich region located on the insulator region of the nickelsilicide film, a ratio (N_(Ni)/N_(si)) of a number of nickel atoms(N_(Ni)) to a number of silicon atoms (N_(si)) is equal to or more than1.11.
 47. A nickel silicide formation method according to claim 46,wherein a region of the nickel silicide film located on thesemiconductor region is composed of nickel monosilicide and a region ofthe nickel silicide film located on the insulator region is composed ofnickel-rich nickel silicide.
 48. A nickel silicide formation methodaccording to claim 46, wherein the step for forming the layer structureis consist of alternately forming at least one nickel layer and at leastone silicon layer at a first substrate temperature which does not causethe silicide reaction.
 49. A nickel silicide formation method accordingto claim 48, wherein the silicon layer formed with the step for formingthe layer structure is an amorphous state.
 50. A nickel silicideformation method according to claim 46, wherein the step for forming thelayer structure is consist of co-depositing step of nickel and silicon.51. A nickel silicide formation method according to claim 46, furthercomprising a step of: a step for implementing a preliminary thermaltreatment at a low temperature lower than the second substratetemperature after the step for forming the layer structure and beforethe step of the silicide reaction.
 52. A nickel silicide formationmethod, comprising steps of: a step for forming a layer structurecontaining silicon and nickel on at least one semiconductor region andat least one insulator region on a substrate; and a step of a silicidereaction for forming a nickel silicide film having a nickel monosilicidecomposition on the semiconductor region as well as having a nickel-richcomposition on the insulator region by implementing a thermal treatmentof the layer structure at a second substrate temperature which causes anickel monosilicide reaction, wherein a nickel-rich region located onthe insulator region of the nickel silicide film has a diffraction peakof Ni₂Si in X-ray diffraction pattern.
 53. A nickel silicide formationmethod according to claim 52, wherein a region of the nickel silicidefilm located on the semiconductor region is composed of nickelmonosilicide and a region of the nickel silicide film located on theinsulator region is composed of nickel-rich nickel silicide.
 54. Anickel silicide formation method according to claim 52, wherein the stepfor forming the layer structure is consist of alternately forming atleast one nickel layer and at least one silicon layer at a firstsubstrate temperature which does not cause the silicide reaction.
 55. Anickel silicide formation method according to claim 54, wherein thesilicon layer formed with the step for forming the layer structure is anamorphous state.
 56. A nickel silicide formation method according toclaim 52, wherein the step for forming the layer structure is consist ofco-depositing step of nickel and silicon.
 57. A nickel silicideformation method according to claim 52, further comprising a step of: astep for implementing a preliminary thermal treatment at a lowtemperature lower than the second substrate temperature after the stepfor forming the layer structure and before the step of the silicidereaction.
 58. A nickel silicide formation method, comprising steps of: astep for forming a stacked layer film by alternately forming at leastone nickel layer and at least one silicon layer on a substrate at afirst substrate temperature which does not cause a silicide reaction;and a step of the silicide reaction for forming a nickel silicide filmby implementing a thermal treatment of the stacked layer film at asecond substrate temperature which causes a nickel monosilicidereaction, wherein, in the step for forming the stacked layer film aratio of a total silicon layer thickness to a total nickel layerthickness in the stacked layer film is equal to or less than 1.79.
 59. Anickel silicide formation method according to claim 58, wherein thesilicon layer formed with the step for forming the stacked layer film isan amorphous state.
 60. A semiconductor device fabrication method,comprising steps of: a step for forming a stacked layer film byalternately forming at least one nickel layer and at least one siliconlayer on at least one semiconductor region and on at least one insulatorregion on a substrate at a first substrate temperature which does notcause a silicide reaction; and a step of the silicide reaction forforming a nickel silicide film containing nickel monosilicide, of whichcomposition is different on the semiconductor region and on tileinsulator region, by implementing a thermal treatment of the stackedlayer film at a second substrate temperature which causes nickelmonosilicide reaction, wherein, in the step for forming the stackedlayer film, a ratio of a total silicon layer thickness to a total nickellayer thickness in the stacked layer film is equal to or less than 1.79.61. A semiconductor device fabrication method according to claim 60,further comprising a step of: an etching step for removing thenickel-rich nickel silicide located on the insulator region of thenickel silicide film by etching, thereby forming the nickel silicidefilm only on the semiconductor region with a self-aligning manner.
 62. Asemiconductor device fabrication method according to claim 60, whereinthe silicon layer formed with the step for forming the stacked layerfilm is an amorphous state.
 63. A semiconductor device fabricationmethod, comprising steps of: a step for forming a layer structurecontaining silicon and nickel on at least one semiconductor region andat least one insulator region on a substrate at a first substratetemperature which does not cause a silicide reaction; a step for forminga region having a low crystallity close to an amorphous state located onthe insulator region and a region having a high crystallity located onthe semiconductor region by implementing a preliminary thermal treatmentat a temperature lower than a second substrate temperature; a step ofetching for removing only the region having the low crystallity close tothe amorphous state located on the insulator region; and a step of thesilicide reaction for forming a nickel silicide film with aself-aligning manner only on the semiconductor region by implementing athermal treatment for the high crystallity region remained on thesemiconductor region at the second substrate temperature which causes anickel monosilicide reaction, wherein, in the step for forming the layerstructure, a ratio (N_(Ni)N_(si)) of a number of total nickel atoms(N_(Ni)) to a number of total silicon atoms (N_(si)) existing in a wholelayer structure is equal to or more than
 1. 64. A semiconductor devicefabrication method according to claim 63, wherein the step for formingthe layer structure is consist of alternately forming at least onenickel layer and tit least one silicon layer at the first substratetemperature which does not cause the silicide reaction.
 65. Asemiconductor device fabrication method according to claim 63, whereinthe step for forming the layer structure is consist of co-depositingstep of nickel and silicon.